Coastal Fisheries and Demersal Estuarine Fauna

Oceanography and Marine Environment of the Basque Country Edited by/~. Borja and M. Collins 9 2004 Elsevier B.V. All rights reserved.

Chapter 19 Coastal Fisheries and Demersal Estuarine Fauna Luis Arregi r Esteban Puente ~, Paulino Lucio r Yolanda Sagarminaga a, Ra61 Castro b and Andrrs Uriarte a aAZTI Foundation, Department of Fisheries Resources; Herrera Kaia, Portualdea s/n; 20110 Pasaia (Spain) bAZTI Foundation, Department of Oceanography and Marine Environment; Herrera Kaia, Portualdea s/n; 20110 Pasaia (Spain) CAZTI Foundation, Department of Fisheries Resources; Txatxarramendi Irla; Sukarrieta; Bizkaia (Spain)

19.1. Introduction Fishing is one of the main economic activities that take place within the sea. As a result, society extracts a great quantity of raw material; this produces large profits to the primary extractive and dealer sectors and benefits consumers. However, the activity must be undertaken in a sustainable manner. Thus, it is necessary to guarantee to future generations the existence of this activity (at least as the present generation does nowadays). In prehistoric times, several authors confirm that fishing was taking place in the Basque Country (see Chapter 1 and Merino, 1991). Evidently, the way in which this activity was undertaken is likely to have differed markedly from what happens nowadays. This activity took place at the edge of the sea or in the intertidal zone, where different species of crustacean and molluscs were collected. Even if they are not related to coastal fisheries, the oldest documents about the activities of Basque fishermen go back to the Middle Ages, with many references to whaling in our waters. There are other, less frequent, mentions of the fishing of other species, like red bream and sardines in the port of Bermeo. Finally, in the ordinances of the first fishing associations from the early Middle Ages, documental data about hake (Merluccius merluccius) fishing have been found. Closer to the present time, the first information on ancient fisheries can be found in Los vascos y las pesquerias transatldmticas (1517-1713) (Huxley, 1984); the starting point of these fisheries was the cod fishing (Gadus morhua), firstly in the waters of Scotland and Iceland and later in Newfoundland, where the Basques found whales and began whaling. The first written document relating to cod fishing dates from 1517; the first about whaling, from 1530. As these transatlantic fisheries, which ended abruptly at the beginning of th the 18 century as a result of the Utrecht Treaty, were taking place, the fishing activity along our coasts was based upon two main seasons: winter, focused upon black spot sea bream (Pagellus bogaraveo), and summer, focused on albacore (Thunnus alalunga). Moreover, large amounts of hake and conger (Conger conger) were caught.

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The fish processing industry was promoted in the 18th century (Chapter 1), but it was during the second part of 19th century when this industry started. It was based mainly upon the small pelagic species, caught by the purse seine fleet. At the same time, the steam engine was introduced into the fishing boats, implying great changes together with some positive aspects, like improved security for the fishermen, and some negative, such as an increase in the fishing capacity. This could have contributed to the overexploitation of some fisheries, e.g. the one targeting black spot sea bream. Additional information about historical background on the Basque fisheries can be found in Chapter 1 and in Gracia Cfircamo (2000). The general seasonal pattern of exploitation has been maintained, in a similar way until the present day. Some changes, which have taken place, relate mainly to modifications in the fishing gears, in the fishing boats characteristics and in the availability of the exploited resources. All these factors will be considered in the present Chapter, based upon the information contained in AZTI (2001) and other. Nowadays, fishing in the Basque Country shows a high diversification, in terms of fishing gears, fishing boats, fishing areas, etc. However, in terms of a general classification, there are three main groups of fisheries: (i) coastal small-scale fisheries; (ii) pelagic fisheries; and (iii) trawl fisheries. 19.2. Small-scale coastal fisheries

The coastal small-scale fishing of the Basque Country is regulated by different authorities (Figure 19.1). Based upon the Spanish autonomic system, the competence of fishing regulation in territorial waters is shared between the Spanish State and the Autonomous Community administrations. Therefore, the Autonomous Community of the Basque Country is responsible for fishing regulations for the "interior waters"; these correspond to delimited areas between the coast and an imaginary straight line between the main capes of the Basque coast (see Figure 19.1).

Figure 19.1. Basque Countrywaters division, into internal and external waters, and main fishing ports.

COASTAL FISHERIES

495

Outside this imaginary line and up to 12 miles of territorial waters (known as "extemal waters"), the fishing regulation competence corresponds to that of the Spanish State (Figure 19.1). Furthermore, European Union legislation in fishing matters ranks higher than those described previously, i.e., state and autonomic legislation must adjust their dispositions to those of the European legislation.

19.2.1. Coastal small-scale fleet A large number of small and medium vessels (181) practice small-scale coastal fishing in the Basque Country, using different fishing gears in the fishing grounds close to the coast; they fish during short periods, usually less than 24 hours. Exceptions are fishing trills in which medium size vessels search for albacore in summer and those made by longliners, looking for sharks. The coastal small-scale fleet is characterised by an important variety of vessel types; these range from a few small vessels (without a wheelhouse) known as "motorised launches" to the numerous middle-sized classical vessels (with a wheelhouse) called "hake boats". When considering the technical characteristics of this fleet (Table 19.1), the average vessel size is 12.4 m long between perpendiculars, with 20.5 t of average gross registered tonnage (GRT) and mean engine power of 105.4 Kw. These vessels have small crews (average 3.5 men.vessel-l); the average age of the vessels is high (mean year of construction: 1983) (Table 19.1). Although the distribution of the vessels is uneven, the coastal small-scale fleet is well represented in all the ports of the Basque Country coast. The most important ports (Figure 19.1) for the coastal small-scale fleet are Bermeo (27.6% of the whole coastal small-scale fleet), Hondarribia (9.9%), Getaria (9.4%), San Sebastian (9.4%), Pasaia (8.3%) and Lekeitio (7.7%). Therefore, these six ports provide more than 70% of the total coastal small-scale fleet. A wide range of fishing gears is used by the fleet, in line with the variety of target species exploited. Usually, almost all the vessels use different fishing gears sequentially throughout the annual cycle, in relation to their appropriateness to catch one target species or another. Only in a few cases are some vessels able to use more than one fishing gear during the same day; this is within the compatibility framework of gear usage according to the fishing regulations. The activity of most of the vessels of this fleet, throughout the year helps to establish the ranking of the importance of the fishing gears. This information is presented in terms of the number of vessels using different gears, at one time or another during the year (Table 19.2). The fishing gears used by the majority of the vessels are the handlines for mackerel (Scomber scombrus)(69%) and trolling lines for albacore (60%). Gillnets are used frequently by vessels, particularly the trammel net (41% of the vessels) and gillnet (40%). Other hook lines, of less importance, are: the bottom longline (23%), whose target species is the conger eel; the surface longline (16%), for sea bass; and the semipelagic longline (14%), for hake. 19.1. Technical characteristics of the Basque coastal artisanal fishing fleet (126 vessels). Key: GRT= Gross Registered Tonnage. Table

Average Standard deviation Maximum Minimum

Length 12.4 4.5 26.0 5.0

GRT 20.5 19.0 99.5 1.0

Kw 105.4 78.2 368.0 6.0

Crew 3.5 1.9 9 1

Construction Year 1983 9.9 1999 1960

m

ii

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Table 19.2. Fishing gears used by the Basque coastal artisanal fishing fleet, with their names in different languages, together with their importance in relation to the number of vessels using them (a sample of more than 100 vessels, whose annual fishing activity has been characterised). Use

Spanish

Basque

English

~no vessels/

%

Linea de mano Linea curric/m Trasmallo Beta Palangre de fondo Palangre de superficie Palangre semi-pel~gico Red de arrastre de fondo de vara Nasas Palangre de deriva Lineas para carla Rasco Red de cerco

Eskuko aparejua Atunetako eskuko aparejua Hirumallako sarea Mallabakarra Hondoko tretza Azaleko tretza , Ur erdiko tretza/Arri-bola Porteria Otarre Marraxotako tretza Pintxo kanabera Zapo sarea In~uratze sarea

Handlines Lines/trolling Trammel net Gillnet Bottom longline Surface longline Semipelagiclongline Bottom beam trawl Pots/Traps Drifting longline Pole and line Tangle net Purse seine

104 90 62 61 35 25 22 22 11 8 7 4 3

69.3 60.0 41.3 40.6 23.3 16.6 14.6 14.6 7.3 5.3 4.6 2.6 2.0

A reduced number of vessels concentrated in the ports of East Gipuzkoa (14% of the total) use bottom beam trawl to collect clumps ! of the red alga Gelidium sesquipedale (see Chapter 18). The least used gears by this fleet (less than 8% of the vessels) are pots (to catch velvet swimming crab and lobster), as well as pole and line. The latter were used widely in the past by the Hondarribia fleet to catch hake, but the stock decline of this species led to a drastic reduction in the use of these lines. Purse-seine is used by this fleet for anchovy (Engraulis encrasicolus), although marginally, and tangle nets (targeting monkfish -Lophius spp.-) are used occasionally by a few vessels located in Santurtzi and Bermeo, respectively. Finally, the use of the drifting longline should be noted; for this, the main target species is the blue shark (Prionace glauca). This is a gear used by a few vessels concentrated in the port of Ondarroa; its catches represent a large amount of the target species.

19.2.2. Species landed Coastal small-scale fishing is characterised by the wide variety of target species, with very disparate weight and economic importance. This diversity is due to the adaptivity of the fleet, depending upon the seasonal availability of the different species, together with the commercial opportunities that market offers. Table 19.3 shows the landings by weight and the estimated value of the first sale on the fish market. It shows the thirty main species classified by both concepts, from greater to lesser importance. Some categories correspond to groups of two or more species; this is due to physical or commercial similarity as they are not distinguished in the fishermen's guilds sales notes, from where these data are taken. Considering the estimated total unloaded weight, per species and per coastal artisanal fleet in 1999, mackerel is by far the main species (77.9% of the weight landed). It is followed in weight importance, but with a considerable difference, by albacore or white tuna (10.2%) and the alga Gelidium sesquipedale (4.7%). The remainder of the species are landed in comparatively small proportions; among these the blue shark (2.3%) occupies an important position. Other important species forming a part of the main target of the coastal small-scale I Clumps: name of bunches of algae torn from the rocks during storms and moved over the seabed, in response to the currents.

COASTAL FISHERIES

497

fisheries, although with considerably smaller landings, are hake (1.3%), conger eel (0.5%), monkfish (0.3%), and bib (Trisopterus luscus) (0.2%). Considering the total estimated value of the landings at first sale in 1999, the economically most important species for the coastal small-scale fleet is albacore (46.8% of the total); the second most important is mackerel (27.6%). These two species, together, represent over 50% of the total first sale value of this fleet. Other important species are hake (10.8%) and, at a lesser degree, blue shark (2.7%), monkfish (1.5%), red mullet (1.2%), sole (1.1%), sea bass (0.9%), and conger eel (0.9%). Table 19.3. Annual estimated landings, per species, of the Basque Country coastal small-scale fleet in 1999.The 30 species with the greatest unloading weights values, in descending order (let~ hand side of the Table). Estimated first sale values for landings of the 30 species, in descending order (fight hand side of the Table). Note: Mullus spp.: Mullus surmuletus and Mullus barbatus; Scorpaena spp.: Scorpaena notata, Scorpaena porcus and Scorpaena scrofa; R.ajidae: Raja undulata, Raja clavata and Raja montagui; Triglidae: Trigla lucerna, Aspitrigla obscura and Aspitrigla cuculus; Scyliorhinidae: Scyliorhinus canicula and Scyliorhinus stellaris; Lamnidae: Latona nasus and lsurus oxhyrinchus; Phycis spp.: Phycis phycis and Phycis blennoides. Latin name

Scomberscombrus Thunnus alalunga Gelidium sesquipedale Prionace glauca Merluccius merluccius

Conger conger Trisopterus luscus Octopodidae Lophius piscatorius Galeorhinus galeus Mullus spp.

Lophius budegassa Diplodus vulgaris

Lamnidae Rajidae Dicentrarchus labrax Scorpaena spp. Solea vulgaris Thunnus obesus Cancerpagurus Sepia officinalis Triglidae Thunnus thynnus Sparus aurata

Sarda sarda Trachurus trachurus

Weight ~Tonnes) 15,829.4 2,070.4 952.2 458.0 264.5 93.7 58.2 46.9 43.2 32.9

% of total 77.9 10.2 4.7 2.3 1.3 0.5 0.3 0.2 0.2 0.2

Latin name

Thunnusalalunga Scomberscombrus Merluccius merluccius Prionace glauca Mullus spp.

Soleavulgaris Dicentrarchuslabrax Congerconger Lophiuspiscatorius Gelidiumsesquipedale

Value ~x 1000 ~

% of total

Mean price ~fKg)

11,900.5 7,018.8 2,754.7 674.1 312.4 282.9 237.3 222.2 211.8 207.5

46.8 27.6 10.8 2.7 1.2 1.1 0.9 0.9 0.8 0.8

5.7 0.4 10.4 1.5 11.5 15.9 11.4 2.4 4.9 0.2

207.2 172.3 141.6 124.3

0.8 0.7 0.6 0.5

10.1 6.7 3.0 9.4

111.7 85.2 79.7 71.3 63.9 61.8

0.4 0.3 0.3 0.3 0.3 0.2

4.5 3.5 1.4 20.8 1.9 4.1

27.2 25.7 24.9 24.1

0.1 Scorpaena spp. 0.1 Lophiusbudegassa 0.10ctopodidae 0.1 Sparus aurata

22.1 20.8 20.6 17.8 16.4 16.1

0.1 0.1 0.1 0.1 0.1 0.1

15.8 15.1 13.7

0.1 Rajidae 0.1 Sepiaofficinalis 0.I Cancerpagurus

49.9 37.5 36.1

0.2 0.1 0.1

2.3 2.4 2.2

13.2 11.3

O.1 Pollachiuspollachius O.1 Thunnusobesus

31.9 31.5

O. 1 O.1

3.2 1.9

Diplodus vulgaris Lamnidae

Trisopterus luscus

Nephrops norvegicus Galeorhinus galeus Triglidae

10.0

0.0 Thunnusthynnus

29.9

0.1

2.2

Pollachius pollachius Pagellus acame

9.9 7.4

0.0 Phycis spp. 0.0 Phycis blennoides

23.3 21.4

0.1 0.1

6.1 4.5

Scyliorhinidae Katsuwonuspelamis Others ~>52 spp.) Total

7.3 6.8

0.0 Pagellus acarne 0.0 Epinephelus guaza

20.2 19.0

0.1 0.1

2.7 20.7

135.4

20,310.8

0.7 Others (> 52 spp.)

100

Total

822.0

0.7

25,430.6

100

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ARREGI, PUENTE, LUCIO, SAGARMINAGA, CASTRO AND URIARTE

19.3. Pelagic fisheries 19.3.1. The purse seine and bait boat fleet Since the first half of the 20 tri century, a fleet of purse seiners developed and evolved in the fishing of small pelagic species (sardine -Sardina pilchardus-, anchovy, mackerel and horse mackerel -Trachurus trachurus-), operating from coastal areas to others beyond the continental shelf (Gaur, 1970). Traditionally, this fleet operates on small pelagics during late winter and spring (March to June); during the summer months (Igelmo et aL, 1984), about 88% of these vessels change to tuna fishing, using small pelagic fishes as live bait. The target species for the tuna fishery is albacore (69% of the vessels) and bluefin tuna (Thunnus thynnus) (31% of the total). Only a small part of the catches of these vessels is obtained inshore within the Basque Country, as much of their activities usually take place farther offshore. Nevertheless, the fleet routinely visits several coastal fishing grounds at the beginning of each week, before moving offshore. These coastal areas are located usually close to fiver mouths and are inhabited typically by small anchovies and horse mackerel in spring (Uriarte and Motos, 1992, 1993). Spawning of anchovy usually takes place partly on these coastal grounds, which in autumn are nursery areas for sardine and anchovy recruitment (Martin, 1989; Motos et al., 1996). Since the 1960s, the Basque purse seine fleet has been reduced progressively; this is due to a discontinuous, but pronounced, reduction in catches, particularly of anchovy (Uriarte and Astudillo, 1987). In 1968, there were about 242 purse seiners, in the Basque Country; by 2001, they had been reduced to only 90. Other reasons for the reduction of the purse seine and live bait fleet are (Santiago et aL, 1996): (i) little restructuring of the fleet; (ii) scarce generational renewal; and (iii) the stabilisation of market prices. Typical purse seiners in 1997 had an average length of 24 m and were about 15 years old (Table 19.4). In more recent years, there has been an increasing effort to renew the fleet. 19.3.2. Species landed Amongst all the pelagic species most intensively fished by the Basque purse seine fleet, albacore, anchovy and mackerel are the most important, in terms of total catches and economical income (Santiago et al., 1996; AZTI, 2001, 2002a) (Figure 19.2). Anchovy catches Global captures of anchovy in the Bay of Biscay have historically been highly variable. Maximum catches were reached in the 1960s (80,000 t). Later, the total catches of the French and Spanish fleets suffered a discontinuous, though pronounced, decrease until the mid 1980s (to less than 10,000 t). During the last decade, the incorporation of a new fleet (French mid-water trawlers) and the success of several recent recruitments (Uriarte et al., 1996) have allowed a gradual increase in global catches, remaining at between 20,000 and 40,000 t. Table 19.4. Technical characteristicsof the Basque Countrypurse seine fleet, in 1997 (134 vessels). i

Mean Standard Deviation Minima Mfi.xima

GRT 107.5 36.6 20 160

I-IP Length 5 2 8 . 4 24.1 213.2 4.0 100 13 900 31

Crew 14.5 2.8 8 18

Construction Year 1972 9.5 1959 1996

COASTAL FISHERIES

499

CATCHES

INCOMES

Others 5%

Mackerel 2%

Mackel 22% Albacore 46%

Ant, ,vvy 27%

Others 3%

Anchov 28%

Mbacore 67%

Figure 19.2. Purse seine percentage of species caught and corresponding incomes, for a selected sample of Basque purse seine vessels, from 1991-1994 (from Santiago et al., 1996). In the past years, anchovy landings in the Basque Country have, fluctuated between 15,000 and 20,000 t (more than 17,000 t in 2000 and 2001) (Figure 19.3). However, during certain years the catches are reduced, mainly because of the adverse environmental conditions, which reduce the efficiency of the vessels. These captures represent 8~;-90% of the total Spanish landings and around 45% of international catches. A recent analysis undertaken on the anchovy stock in the Bay of Biscay shows that the population remains inside safe biological limits in recent years (ICES, 2002).

Figure 19.3. International anchovy catches, since 1940, in the Bay of Biscay, overlaying the level of French and Spanish catches and those landed in the Basque Country.

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Tuna catches The albacore is one of the most important species for the Basque coastal artisanal and pelagic fisheries. In 2000, the total albacore landings reached 9,600 t. Captures of this species are realised mainly in the Bay of Biscay and adjacent waters, although the spatial distribution of this fishery may reach up to 25~ Catches by the Basque fleets represent about a half of the total Spanish captures, and 30% of international landings in the north Atlantic. Historically, the northern stock captures have decreased sharply, from 60,000 t landed in 1965 to 34,500 t in 1999. Nevertheless, landings by the Basque fleet have remained stable during this time, at around I0,000 t (Figure 19.4). Analyses carried out on the albacore stock situation have indicated that this stock does not appear to suffer from overfishing, although fishing mortality in juveniles showed an increasing trend during the last years (Anon., 2001). The bluefm tuna fishery is less important in the Bay of Biscay; nevertheless, it is of great importance for some of the Basque ports, particularly for the vessels from Hondarribia (see Figure 2, in Preface). Bluefin tuna fishing is practiced by the tuna boats using mainly small horse mackerel as live bait. In the Basque Country the average bluefin tuna landings reach about 2,200 t per year, which represent more or less 30% of the catches in the eastern Atlantic and 8% of the total eastern stock catches (including the Mediterranean). The present international level of captures is not sustainable and leads to an overfishing of the eastern bluefm tuna stock (Anon., 2002). Mackerel horse mackerel and sardine catches The mackerel represents also, in terms of abundance, one of the most important pelagic fisheries for the Basque fleets (adding up the coastal artisanal and pelagic purse seine landings together). Most of the catches are obtained during the early spring and consist of adult spawning mackerel (Villamor et aL, 1997). Catches of the Basque fleet have increased slightly during the 1990s and, over the last five years, they have fluctuated between 15,000 and 25,000 t. This amount accounts for about 50% of the Spanish catches, but it is only around 2-3% of the international catches. The northeast Atlantic mackerel lies within safe biological limits, although fishing mortality is just above the sustainable precautionary levels (ICES, 2002).

Figure 19.4. Catches of albacore landed in the Basque Country, in comparison with those produced in Spain and over all of the North Atlantic.

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Sardine and horse mackerel are economically less important species for the Basque purse seine fleet. Captures of sardine and horse mackerel take place mainly during spring, coinciding with the mackerel and anchovy seasons, also in summer and autumn. These captures represent less than 5% of the total species captured by this fleet; they account for less than 3% of the income generated by this particular activity. Sardine captures by the Basque fleet along the Cantabrian coasts (ICES Division VIIIc, Figure 19.5) and during recent years (1,000-4,000 0 represented about 10% of the Spanish catches in this area (around 14,000 t, in 1999 and 2000). Nevertheless, sardine landings by the Basque fleet have increased since 1996 in the eastern Bay of Biscay (ICES Division VIIIb, Figure 19.5), with captures close to 8,000 t which represent 30% of the global Spanish captures. Regarding the safe biological limits the stock situation is not clear. Nevertheless, fishing mortality has decreased since 1998, whilst the spawning stock biomass remains stable.

Figure 19.5. Map of the International Council for the Exploration of the Sea (ICES) fishing Sub-areas and Divisions.

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ARREGI, PUENTE, LUCIO, SAGARMINAGA, CASTRO AND URIARTE

Finally, the Basque fleet exploits two different horse mackerel stocks, the western and the southern stocks. Landings from the western stock, by the Basque fleet, have been very variable in recent years, fluctuating between 700 and 5,000 t; this represents a minimum part of global international catches in this area (137,000 t in 2000). This stock is considered to be inside safe biological limits; nevertheless, fishing mortality is very high, taking into account the low recruitments in the last few years. On the other hand, the southern stock is not as abundant; however, it seems to be more stable, throughout time. The Basque fleet captures on this stock have remained quite stable during the last decade (at between 2,000 and 3,000 t). 19.3.3. Fisheries activities and seasonality Small pelagic fisheries are changing their target species, as the season progresses (Table 19.5). In February, after the winter resting, the purse seine fleet starts fishing sardine and mackerel. This fishing is coincident with the reproductive season of these species in the area. Since the mid-1990s, catches of mackerel have increased considerably, due to the incorporation of the Cantabrian purse seiners into this activity. The increases in market prices because of the reduction of TAC (Total Allowable Catch) in 1996, together with the increases of spawning biomass in the southern areas in the late 1990s, favoured the rise in the mackerel catches. With a total of catches of 41.7 t in 1999, the mackerel represents the most important fishery among the small pelagic species in the area. However, from an economical point of view, these captures represent only 9% of the total income of this fleet. The mackerel fishing reaches the peak captures in March. Later, there is a continuous reduction in catches, until May; this is followed by a parallel increment in the anchovy captures. The Spanish anchovy catches are achieved almost entirely during spring and early summer, from March to June. This is the spawning period of the species and the purse seiners obtain about 90% of the annual Spanish catches. These catches are made within the southeastern comer of the Bay of Biscay, often not far from the coasts of the Basque Country and Cantabrian regions, where most of the purse seiners have their home ports. Purse seiners fish usually at night, when anchovy move up to the surface to spawn. Spanish catches during the second half of the year are very low and are achieved mainly in the central and western areas of ICES Division VIIIc (Figure 19.5) and in the recent years in the northern part of the Bay of Biscay, in IXa in autumn. This secondary campaign for anchovy has been more important since 1996, when the Spanish fleet obtained free entrance into French waters (outside the 12 nautical miles of territorial waters) to catch the unfished quota of anchovy. Economically, the anchovy fishery is the second funding source for this sector; their catches represent about 28% of the total income. In summer, there is a Spanish fishery for anchovy, to be used as live bait for tuna fishing. However, these catches are very low, compared to the commercial fishery (ICES, 2002). Table S

19.5. Seasonalityof the different specific purse seine fleet fisheries. ,

Horse mackerel Sardine Mackerel Anchovy Tuna

Jan Feb

Mar

At~r May Jun

Jul

Au2

SeD

Oct

Nov

Dec

COASTAL FISHERIES

503

Sardine and horse mackerel fisheries are not economically significant for the Basque purse seine fleet; they are considered as secondary species. Captures of sardine and horse mackerel take place partly during spring, coinciding with the mackerel and anchovy campaigns, and more secondarily during the second half of the year. This capture represents less than 5% of the total species captured by this fleet; it is less than 3% of the income generated by this particular activity. Albacore is the most important economical resource for the Basque purse seine and bait boat fleet. The albacore fishing extends from July to October, achieving the peak captures during the summer months. This period corresponds to the annual migration of young individuals (1-4 years old) for feeding in the Bay of Biscay and to the south of Ireland. In these areas, the Basque bait boats obtain about 90% of the total albacore catches. On the whole, the albacore captures distribution follows the migration pattern of this species. The fishing of albacore extends into the middle of December in the Mediterranean Sea and to the southeast of Portugal; this reduces, therefore, the inactivity period for this fleet to the winter months (December-March). The economical importance of bluefin tuna is lower than that of albacore, for Basque fishermen. However, for many Basque ports (like Hondarribia) it represents the main founding resource of the fleet. The .fishing season is somewhat longer thgn that described for albacore. Bluefin tuna are fished for in the Bay of Biscay during its feeding migration, mainly from June to November.

19.3.4. Recent research on pelagic fisheries, using satellite imagery Since 1978, when the first oceanographic satellite (SeaSat) was launched, a great amount of useful environmental information, on a global scale, has been provided by earth observation sensors on board several satellite platforms launched throughout all these years. Amongst the several oceanographic applications, the study of environmental variables affecting fisheries distribution has lately assumed importance. This information is being required increasingly by fishery professionals for 'fast fish target' detection purposes. This observation is particularly relevant for highly migratory species, like tuna, which are distributed over vast areas difficult to cover by local fishing fleets. On the other hand, the overall decline of the commercial fish stocks causes an increasing concem for obtaining a detailed understanding of fish ethology in relation with the environment; this is required in order to manage properly these stocks, and to have a basis for ensuring their sustainability. The application of remote sensing data to study the distribution of fish can be directly applied to fish species living in the upper water layers, such as tuna (Figure 19.6); this is because the environmental information provided by most of the remote sensors, is restricted to the ocean surface. AZTI has applied this technology to the study of the tuna catches and the main thermal features, such as fronts. Nevertheless, a different type of information is provided; this may be complementary and very useful for the interpretation of the environmental dynamics of the ocean areas studied. Amongst the principal sources of satellite data are the AVHRR (Advanced Very High Resolution Radiometer) data, operated by National Oceans and Atmosphere Administration (NOAA) of the United States, on board the series of their polar satellites. This sensor provides information on the visible and thermal infrared part of the spectrum but, for oceanographic purposes, the infrared channels are the most used for estimation of Sea Surface Temperatures (SST). SST images are valuable to monitor the thermal evolution of ocean surface related to

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ARREGI, PUENTE, LUCIO, SAGARMINAGA, CASTRO AND URIARTE

Figure 19.6. NOAA 12 image (23thAugust, 1999) showingthe albacore (circles: large >200 individuals; small < 20 ind.) and bluefin (squares: large >20 ind; small: <4 ind) catches, related to SST, in the Bay of Biscay. seasonality; they depict meso-scale events revealed by their specific thermal characteristics i.e. upwellings, eddies, thermal fronts, fiver plumes, etc. (see Chapters 5, 7 and 8). For ocean colour estimation and related products, such as the concentration of chlorophyll-a distribution, the Coastal Zone Color Scanner (CZCS) has provided (from October 1978 to June 1986) the first important source of data. This mission revealed the great potentiality of these data; new missions were projected with improved instrumentation. As a result, the SEAWIFS sensor was launched in 1997, by NASA. More recently, other satellites have been launched; these include sensors which gather data with all the most interesting channels for oceanographic and fisheries applications. The most important of these satellites are the United States MODIS (Moderate Resolution Imaging Spectroradiometer) aboard the Terra (EOS AM) and Aqua (EOS PM) satellites launched in December 1999 and the European MERIS (MEdium Resolution Imaging Specrometer Instrument), on board the Envisat satellite, launched in March 2001. The main product generated from visible channels, included in all these sensors, is chlorophyll-a concentration; this provides direct information about the areas where important primary production is taking place and where a trophic chain is, therefore, likely to be formed, influencing the distribution of pelagic fishes. Colour images may be used also as tracers of some oceanographic events, such as eddies, fronts, etc.; these, in turn, are affected by transport processes and the distribution of phytoplankton and/or suspended sediments. Other important data sources, whose exploitation for fisheries application have been more recent, are altimeter and scatterometer data. The principle altimeter data come from the

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TOPEX/POSEIDON and ERS1/2 missions and scatterometter data are provided mostly by Seasat (SASS), ERS-1/2 (ESCAT), ADEOS (NSCAT), and .QuikSCAT (SeaWinds or

QSCAT). Both altimeters and scatterometers are active sensors working in the microwave range of the spectrum. Altimeters provide information on the sea surface height, related to the ocean circulation and density distribution of water masses (see Chapters 6 and 7). Scatterometers measure oceanic surface winds, which constitute the main driving force of surface meso-scale circulation, of a regional area (see Chapters 4 and 5). Thus, the spatio-temporal behaviour of many pelagic fish species is very much related to the spatio-temporal dynamics of different environmental parameters depicted by the different satellite-derived data. However, these relationships vary between different species and regions. The majority of the studies about the relationship between pelagic fish distribution and satellite imagery deal with tuna species, because of their great commercial interest and their somewhat vast extent. For example, Laurs et al. (1984), using AVHRR and CZCS, demonstrated the role of oceanic frontal structure in the habitat and migration pattern of albacore. Elsewhere, Reddy et al. (1995) used satellite-derived sea surface temperatures to show that tuna and albacore off Tasmania are related to warm-core eddies and strong thermal fronts. Similar results have been described by other authors for bluefin tuna and yellowfin tuna off western Australia and off the coast of India. Other studies have considered the distribution of spawning grounds of small pelagic species such as anchovy and fish early life stages distribution and survival. For example, the spawning habitat for northern anchovy in the southern California Bight can be defined using a combination of satellite-derived SST and surface chlorophyll distributions (Lasker et aL, 1981; Fiedler, 1984). In the Gulf of Mexico, larval fish assemblages have been related to the 'loop current boundary', determined by satellite images (Richards et aL, 1993); AVHRR satellite imagery played an important role in the investigation of the distribution and advective transport of fish larvae over the continental shelf off North Carolina (Govoni and Pietrafesa, 1994) In the Bay of Biscay, studies about the distribution of temperate water tunas, such as albacore and Atlantic bluefin tuna, are presently underway. In the same way, satellite data have been used to study the spatio-temporal dynamics of anchovy spawning in spring and the distribution of juveniles in September. Such studies have confirmed the relationship between spawning and the rise in temperatures along the Bay of Biscay, revealing the important advective processes of early life stages, which transport the majority of juveniles to offshore grounds (Uriarte et al., 2001 a, b). For different reasons, satellite products have been less exploited for littoral fisheries resources in the Basque region. On the one hand, the main pelagic fishes (from their socioeconomic interest point of view) are distributed far away from the littoral. Ort the other hand, for those distributed along the littoral, their area of distribution is not especially extensive and is quite constant; thus, interest in satellite data is limited.

19.4. Biology of the main target species and related environmental aspects The presence of species exploited in the Basque littoral varies seasonally, depending upon the biological and ecological behaviour of these populations. The anchovy population, which inhabits this area, belongs to the Bay of Biscay population, which is considered independent from the populations of anchovy found in more northern or southern areas in the Atlantic Ocean (Uriarte et al., 1996). The possibility of this

506

ARREGI, PUENTE, LUCIO, SAGARMINAGA, CASTRO AND URIARTE

population being composed by sub-populations cannot be discarded (Junquera and P6rez G~indaras, 1993). Anchovy often forms shoals close to the bottom.during day time and in the upper layers at night (Mass6, 1996). Anchovy can live for up to 5 years (Uriarte and Astudillo, 1987), but the fisheries exploit mainly the 1-3 age groups. There is a limited amount of pelagic spawning in spring, on which extensive biological studies have been undertaken (Sanz and Uriarte, 1989; Motos et aL, 1996) in order to apply the Daily Egg Production Method to estimate the biomass of the population (for further details, see Chapter 17). Although the sardine found in the Basque littoral zone belongs to the Iberian Peninsula stock (ICES Divisions IXa and VIIIc; see Figure 19.5), some catches are made beyond the limits defined for this stock (in Division VIIIb). Connections between the sardine populations from the Iberian Peninsula stock and those inhabiting areas more to the north or to the south are poorly understood (ICES, 2002). Sardine is a small pelagic cupleoid, living up to 12 or more years (Porteiro and Alvarez, 1985); however, the fishery exploits all the population above the 2-5 age groups. In particular, sardines caught in the Basque Country are generally larger and older than those caught in the western area of the Division VIIIc, or in Division IXa (Figure 19.5). The spawning of this species occurs in winter and early spring (see Chapter 17) and its spawning biology (P&ez et al., 1992) has been studied by applying the Daily Egg Production Method to monitor the abundance of the resource around the lberian Peninsula (see Chapter 17). The mackerel found in the Basque littoral belongs to the so-called North East Atlantic mackerel population (NEAM), which extends all along the western margin of Europe, from Portugal to Norway (ICES, 2002). In 1995, the Advisory Committee on Fisheries Management (ACFM) of ICES agreed to distinguish a western (VIIIa,b,d) and a southern spawning component (VIIIc and IXa) (Figure 19.5). Catches made in the Basque Country are allocated mostly to the southern component of the NEAM. Tagging undertaken offshore of the Basque Country (Uriarte and Lucio, 2001) has demonstrated that southern mackerel spawners follow common migratory routes, with the western component towards the North Sea and Norwegian Sea~ during the summer. Therefore, mackerel from the different components mix and are caught together most of the year; hence, the fisheries are not separable and the assessment has been unified by ICES. Mackerel are distributed near the sea surface in enormous shoals. Compared to other pelagic species, their growth during the first months of life is very fast; they reach a length over 10 cm two or three months atler the spawning peak in this area. Mackerel live up to 20 years, but most of the oldest individuals found are about 12-15 years old. The fork length exceeds commonly 30 cm, with a maximum of 50 cm. Females of the species grow larger than males (Lockwood, 1988). Spawning takes place in late winter and early spring (Lago de Lanz6s et al., 1993) in the southern region (Division VIIIc), where the Basque purse seiners operate._The southern pre-spawning migration pattern of Atlantic mackerel is directed towards areas with low turbulent mixing at spawning time, providing a "stable environment" for egg and larval survival (Borja et al., 2002). In the southern areas, where the spawning starts, the turbulence conditions of pre-spawning and spawning periods has the largest influence on the success of recruitment; this could be related to the more 'stable' weather in the subsequent months and for the remainder of the year. In contrast, in the northern areas, the role of turbulence over the entire year becomes increasingly more relevant; this is most likely related to the high levels of turbulence during autumn.and winter, which limit the survival of juveniles. About 50% of the variability in the Atlantic mackerel recruitment may be explained by means of environmental

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507

variables, such as turbulence; other variables, such as upwelling and North Atlantic Oscillation (NAO), are only slightly, or are not, statistically significant (Borja et al., 2002). Horse mackerel is distributed all along the European coasts, from Norway to Portugal. The population found in the Basque littoral belongs mainly to the European southern stock. The species may be considered as benthopelagic; it is found often over sandy bottom, at 100200 m depth, but occasionally also at near-surface. Horse mackerel is distributed in large shoals near the coast in the warmest months of the year; it moves to deeper waters in the winter. On the average, this species lives 15 years, but may live up to more than 20 years and can reach a size to about 60 cm fork length, with common sizes ranging from 15 to 30 cm. The peak in spawning of all these species in the Basque littoral shows the following seasonal sequence: (i) sardine from early spring, March and April; (ii) mackerel from midspring (April and May) to late spring; and (iii) anchovy and horse mackerel in May and June. Sardine, mackerel and horse mackerel spawn over the continental shelf edge and over the continental shelf of the entire Bay, including the coastal areas of the Cantabrian Sea (Arbault and Lacroix, 1968; Lago de Lanz6s et al., 1993). Anchovy and horse mackerel use also these areas for spawning, but the most important spawning areas for anchovy (used partly by sardine, as well) are the coastal areas influenced at the surface by lower salinity waters caused by fiver outflows: (i) the zones of influence of the large French rivers (Gironde and Adour), and (ii) secondarily, many smaller Cantabrian rivers (Motos et al., 1996). Shelf breakfronts and river plumes are typically productive-enriched areas during spring, which may favour spawning activities (Chapters 7, 8 and 17). Anchovy larvae survival is favoured by weak upwelling events, during spring and early summer (Borja et al., 1996, 1998) (Figure 19.7). This pattern is related also to the expansion of the river plumes towards the east. By summer, these surficial low salinity layers 1800

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508

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are usually poor in chlorophyll and depleted in nutrients, due to their being consumed during the spring phytoplankton bloom (see Chapters 7 and 8). A sub-surface chlorophyll maximum is located under the thermocline (Valencia, 1993; Valencia et al., 1996). Gales and storms during late spring and early summer may delay the establishment of the final summer stratification, affecting negatively the survival of developing fish larvae, as proposed for anchovy (Allain et al., 1999). Recent studies show that the bulk of juvenile anchovies present in September, 3-4 months atter the peak spawning, inhabits the upper layers of the drit~ing low salinity waters (Uriarte et al., 2001a, b). These waters are relatively "old" and depleted waters, some time after their spreading out from coastal areas under the influences of fiver discharges. Ttiis is the first time that offshore distribution of the juveniles in September is related directly with the well-known spring spawning areas; these are influenced, at the surface by some of the major fiver plumes in the Bay of Biscay (such as the Gironde, Adour and Cantabrian rivers) (Motos et aL, 1996). This situation serves to build up a spatial framework, for the onset of the early recruitment of anchovy in the Bay of Biscay. This westward drifting of the early phases of juvenile anchovies matches the scheme of recruitment discussed in Borja et aL (1996). These authors, in addition, related the final success of the recruitment to the strength of the upwelling regime in the Bay from March to July. Both processes are related, in a sense, to the northeasterly winds prevailing during spring, particularly in June and July, causing the displacement of coastal waters towards the west or southwest and provoking the upwelling regimes of spring and early summer (see Chapters 4, 7 and 8). Tuna, bluefin ttma and albacore cannot be considered as species inhabiting the Bay of Biscay, as they visit the Basque littoral in their trophic migration routes. The specimens going into the Bay are immature individuals that migrate from the African coast (bluefin tuna) or Azores (albacore) to the feeding areas during the summer months; they return again to these areas during the autumn. Santiago (1997) and Borja and Santiago (2001) have studied the relationships between some environmental processes generated by the NAO and the recruitment of three tuna stocks: western and eastern bluefin and northern albacore. The conditions of the NAO control the temporal fluctuations in the speed and direction of the surface westerlies across the mid-latitudes of the North Atlantic. These, in turn, influence the temperature, precipitation and biological aspects of oceanography, such as recruitment. Regression analysis indicates statistically significant relationship between the NAO and the eastern bluefin tuna recruitment, at the 95% confidence level, and at the 99% level in the case of northern albacore. No significant relationship exists between the NAO and western bluefin tuna recruitment. The relationship of the NAO with the eastern bluefin tuna is direct, whereas it is inverse for northern albacore. 19.5. Demersal fauna in estuaries

Apart from the species of commercial interest, a community composed of small fishes and macrobenthic fauna (clams, crabs and shrimps) also exists within the estuaries. The gear employed to capture this demersal fauna defines it well: the beam-trawl, which catches swimming fishes and shrimps, wandering crabs and borrowing clams and worms. Estuarine communities are composed mainly of marine species that enter with high tide and those adapted to changing salinity; they feed on fiver discharges and high productivity in the transitional zone. The longest series of data concerning demersal fauna in Basque estuaries belongs to

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the Bilbao-Bizkaia Water Consortium, which started regular surveys in 1989 in the Nervi6n and Barbadun estuaries (AES, 1989); these continue nowadays (Franco et al., 2001a). Apart form that, the Local Water Authority of Gipuzkoa studied demersal fauna of fiver mouths, in 1987-1988 (1NSUB, 1988), 1995-1996 and 2001 (AZTI, 1996, 1997, 2002b). Estuaries in the Basque Country are usually very small and sustain only a reduced community. The commonest species are shore crab (Carcinus maenas) and two gobies, sand goby (Pomatoschistus minutus) and black goby (Gobius niger), which are present in all the river mouths. Brown shrimp (Crangon crangon) is an opportunist species, which shown locally very high abundance, but is absent from many areas. Common prawn (Palaemon serratus) has a more homogeneous distribution. Grey mullet (Chelon labrosus) is a fish "that reaches the lowest weirs in rivers and feeds on floating particles, breathing surface-dissolved oxygen. In less polluted waters, grey mullet eats green algae growing on the rocks. Finally, the glass-eel (Anguilla anguilla) enters by the tide, during autumn and winter nights, following the call of the fiver outfall. Some young eels live in the estuaries or come to feed there for years, before they start their nuptial trip to the breeding area at the Sargassum Sea. Grey mullet and eel are the most tolerant species to water pollution; they cross even the most heavily contaminated areas, searching for food and river water. Flounder (Platichthysflesus) is also a coastal fish reaching the rivers. Swimming over the bottom, this species is sensitive to pollution and may be used as an indicator of the quality of the estuary. Cockle (Cerastoderma edule) and clam (Ruditapes decussatus) are endobenthic species appearing in sandy sediment of the middle estuary, while fiat clam (Scrobiculariaplana) is more abundant in muddy tidal beaches, and trawls catch only empty shells. Another common benthic species is the worm Hediste diversicolor (for additional details, see Chapter 18). It is convenient to distinguish the estuarine from the littoral species, whose presence in surveys indicates only the influence of marine conditions. This pattern is the case for the large harbours or embayments (Txingudi, Pasaia, Urdaibai and the Abra of Santurtzi) (for locations, see Figure 2, in Preface) and high water conditions. Whelk (Hinia incrassata), small clam (Corbula gibba), cuttlefish (Sepia officinalis), sea mouse (Aphrodita aculeata), swimming crabs (Necora puber and Liocarcinus depurator), small hermit crab (Diogenes pugilator), spider crab (Macropodia rostrata) and, amongst fishes, white bream (Diplodus sargus), dragonet (Callionymus maculatus), red mullet (Mullus surmuletus) and scaldfishes (Arnoglossus spp.) are common species of this kind. The most highly valued species are bass (Dicentrarchus labrax) and sole (Solea vulgaris). As an example, Figure 19.8 shows the distribution of the number of demersal fish species along the Nervi6n estuary, obtained by trawl sampling. The deficit of oxygen in relation to sewage outfalls from industrial or urban origin is the main limitating factor for demersal fauna in the innermost part of the estuary. However, the dimensions and structure of the river banks seem to play also an important role. Channelled estuaries have poorer communities than those with marsh and harbour habitats (see Chapters 18 and 22). Due to the effort of the sewerage plans, which commenced between 1989 and 1995, this factor is now changing. There is a clear recovery of the demersal fish communities in some of the estuaries, such as the Nervi6n (see Figure 19.9) and Oiartzun (Franco et al., 2001 b). For additional details on the recovery of such systems, see Chapters 2 and 22.

510

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References

AES, 1989. Report on monitoring surveys carried out in 1989 on the Abra de Bilbao and the estuaries of the Nervi6n and the Barbad~n. Analytical and Environmental Services, Northumbrian Water Group, UK. Unpubhshed report. Allain, G., P. Petitgas and P. Lazure, 1999. Environmental and stock effects on the recruitment of anchovy in the Bay of Biscay: a multivariate analysis. ICES CM1999/Y:22, 12 pp. Anonymous, 2001. Report of the ICCAT SCRS Albacore Stock Assessment Session (Madrid, Spain - October 9 to 15, 2000). Collect. Vol. Scientific Papers ICCAT, 52: 1283-1390. Anonymous, 2002. Atlantic bluefin tuna executive summary. Informe del periodo bienal 2000-2001. H Parte (2001) 2: 54-68. Arbault, S. and N. Lacroix, 1968. Ichtyoplancton. Oeufs et larves des poissons t61eost6ens dans le Golfe de Gascogne en 1964. Revue des Travaux de l'Institut des P~ches Maritimes, 32(4): 413-476. AZTI, 1996. Estudio de la calidad biol6gica de los sedimentos de los estuarios interiores de los rios Bidasoa, Oiartzun y Urumea. Departamento de Obras Hidrafilicas y Urbanismo de la Diputaci6n Foral de Gipuzkoa. Unpublished report. AZTI, 1997. Estudio de la calidad biol6gica de los sedimentos de los estuarios interiores de los rios Oria y Urola. Departamento de Obras Hidrafilicas y Urbanismo de la Diputaci6n Foral de Gipuzkoa. Unpublished report. AZTI, 2001. AZTI Arrantza 2001. Ed. AZTI, Sukarrieta, 58 pp. AZTI, 2002a, Estudio tdcnico-pesquero y socio-econ6mico de las pesquerias artesanales costeras del Pals Vasco. Unpublished report. Study contract N ~ 99/024. AZTI, 2002b. Estudio de las comunidades de fauna demersal en los estuarios de Oiartzun y Bidasoa. Departamento de Obras Hidrafilicas y Urbanismo de la Diputaci6n Foral de Gipuzkoa. Unpublished report. Borja,/k. and J. Santiago, 2001. Does the North Atlantic Oscillation control some processes influencing recruitment of temperate tunas? ICCAT SCRS/01/33, 19pp. Borja, /k., A. Uriarte, V. Valencia, L. Motos and A. Uriarte, 1996. Relationships between anchovy (Engraulis encrasicholus) recruitment and the environment of the Bay of Biscay. Scientia Marina, 60 (Supl.2): 179-192. Borja, A., A. Uriarte, J. Egafia, L. Motos and V. Valencia, 1998. Relationships between anchovy (Engraulis encrasicolus) recruitment and environment in the Bay of Biscay (1967-1996). Fisheries Oceanography, 7: 375-380. Borja,/k., A. Uriarte and J. Egafia, 2002. Environmental factors and recruitment of mackerel, Scomber scombrus L. 1758, along the north-east Atlantic coasts of Europe. Fisheries Oceanography, 11: 1-12. Fiedler, P.C., 1984. Some effects of el Nifio 1983 on the northern anchovy. California Cooperative Fisheries Report, 25: 53-58. Franco, J.,/k. Borja, R. Castro, O. Solaun, M.J. Belzunce, V. P6rez and F. Villate, 2001a. Seguimiento ambiental de los estuarios del Nervi6n, Barbad(m y Butr6n durante 2000. Consorcio de Aguas Bilbao Bizkaia. Unpublished report. Franco, J.,/~. Borja, O. Solaun, M.J. Belzunce, J. Bald and V. Valencia, 200 lb. Campa~a de medici6n de variables biol6gicas y fisico-quimicas en el estuario del rio Oiartzun y 6rea costera pr6xima a cala Murgita. Diputaci6n Foral de Gipuzkoa, 198 pp. + annexes. Unpublished report. ,

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Gaur, S.C.I., 1970. La pesca de superficie en GuiplJzcoa y Vizcaya, Andlisis y Perspectivas. Informe de Caja Laboral Popular y COPESCA. Bilbao 365 pp. Govoni, J.J. and L.J. Pietrafesa, 1994. Eulerian views of layered water currents, vertical distribution of some larval fishes, and inferred advective transport over the continental shelf offNorth Carolina, USA in winter. Fisheries Oceanography, 3: 120-132. Gracia Cfircamo, J., 2000. Un breve recorrido por la historia de la pesca en el Pals Vasco. Euronews & Media, Digital Journal: http://www.Eusko-irakaskuntza.org/euskonews/ 0064zbk/gaia6404es.html 64 zbkia. (2000/1-28/2-4) Huxley, S., 1984. Itsasoa 3. Los vascos en el marco Atlrntico Norte. Siglos XVI y XVII. Ed. Etor, San Sebastifin, 336 pp. ICES, 2002. Report of the Working group on the assessment of mackerel, horse mackerel, sardine and anchovy. (Denmark, 4-13 September 2001). ICES CM 2002/ACFM:06 Igelmo A., X. Iribar, S. Lerga and J. Legarra, 1984. lnventario de artes de pesca en Euskadi. Centro coordinador de Publicaciones del Gobiemo Vasco. Vitoria-Gazteiz, 305pp. INSUB, 1988. Estudio de las Rias Guipuzcoanas: comunidades de peces y macroinvertebrados. Diputaci6n Foral de Gipuzkoa. Unpublished report. Junquera, S. and G. Prrez-Gfindaras, 1993. Population diversity in Bay of Biscay anchovy (Engraulis engrasicholus, L. 1758) as revealed by multivariate analysis of morphometric and meristic characters. ICES Journal of Marine Science, 50: 383-396. Lago de Lanzrs, A., A. Sola, L. Motos and C. Franco, 1993. Mackerel (Scomber scombrus L.) egg production and stage I egg production estimates in Division VIIlb,c and IXa from 1988, 1990 and 1992. ICES CM/H:44. Lasker, R., J. Pelfiez and R.M. Laurs, 1981. The use of satellite infrared imagery for describing ocean processes in relation to spawning of the northern anchovy (Engraulis mordax). Remote Sensing Environment, 11" 439-453. Laurs, R.M., P.C. Fiedler and D.C. Montgomery, 1984. Albacore tuna catch distribution relative to environmental features observed from satellites. Deep Sea Research, 31" 1085-1099. Lockwood, S.J., 1988. The mackerel Its biology, assessment and the management of a fishery. Fishing Book News Ltd., Famham, Surrey, England. 181 pp. Martin, I., 1989. Catch of small pelagic species by the life bait boats of the Basque Country in 1987 and 1988. ICES CM 1989/H:34. Massr, J., 1996. Acoustic observations in the Bay of Biscay 9 schooling, vertical distribution, species assemblages and behaviour. Scientia Marina, 60(sup. 2) : 227-234. Merino, J.M., 1991. La pesca. Servicio Central de Publicaciones del Gobiemo Vasco, Vitoria. Motos, L., A. Uriarte and V. Valencia, 1996. The spawning environment of the Bay of Biscay anchovy (Engraulis encrasicolus L.). Scientia Marina, 60:117-140. Prrez, N., I. Figueirido and B.J. Macewicz, 1992. The spawning frequency of sardine, Sardina pilchardus (Walb), off the Atlantic Iberian coast. Boletin del Instituto Espa~ol de Oceanografia, 8:175-189. Porteiro, C. and F. Alvarez, 1985. Determinaci6n del crecimiento de la sardina, Sardina pilchardus (Walb), en aguas gallegas, mediante lectura directa de otolitos. Informes T~cnicos del Instituto Espa~ol de Oceanografia, 14:19 pp. Reddy, R., V. Lyne, R. Gray, A. Easton and S. Clarke, 1995. An application of satellite derived sea surface temperatures to southern bluefin tuna and albacore off Tasmania (Australia). Scientia Marina, 59: 445-454.

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