The impact of the hake Merluccius spp. longline fishery off South Africa on procellariiform seabirds

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S 0006-3207(97)00020-7

Biological Conservation 82 (1997) 227-234 © 1997 Published by Elsevier Science Ltd All rights reserved. Printed in Great Britain 0006-3207/97 $17.00 + 0.00

ELSEVIER

THE IMPACT OF THE H A K E Merluccius SPP. L O N G L I N E F I S H E R Y OFF S O U T H A F R I C A O N P R O C E L L A R I I F O R M SEABIRDS

K e i t h N. Barnes,*" Peter G. R y a n a & C h r i s t i a n B o i x - H i n z e n a aPercy FitzPatrick Institute, University of Cape Town, Rondebosch 7700, South Africa

(Received 5 December 1996; accepted 4 February 1997)

Abstract In 1994, an experimental longline fishery for hake Merluccius spp. commenced in the shelf waters off South Africa. Participants were required to record any birds caught, and these data were supplemented by ship-based observers on several vessels. Longlines are set at night, and the white-chinned petrel Proceilaria aequinoctialis was the only seabird species caught while attempting to scavenge bait during gear setting. Small numbers of great shearwaters Puffinus gravis and pintado petrels Daption capense were killed during hauling operations. The hake longline fishery is estimated to kill 8000 + 6400 whitechinned petrels a year in South African waters at a rate of 0.44 birds per 1000 hooks. This represents < 1% of the global white-chinned petrel population, but is cause for concern given (1) the slow reproductive rate among procellariiform seabirds; (2) the projected growth in the longline hake fishery; and (3) the increasing numbers of white-chinned petrels being killed in other longline fisheries. Light intensity was the most important factor for explaining variation in the number of petrels caught during setting; when line shooting was completed prior to the increase in white-chinned petrel activity (c. 2.5 h before sunrise), few birds were caught. Measures to reduce excessive seabird bycatch include: (1) the introduction of bird lines on all vessels; (2) restricting the setting of lines to times of least bird activity; (3) minimum use of deck lighting during setting; and (4) ensuring that baited hooks sink as fast as possible when deployed. Hauling mortalities can be reduced by diverting offal outlets to the opposite side of the vessel to where the longline is being hauled. © 1997 Published by Elsevier Science Ltd

INTRODUCTION

Large numbers of procellariiform seabirds are killed each year when they swallow baited hooks set by longline fishing vessels (Brothers, 1991; Murray et al., 1993; Cherel et al., 1996). Population decreases of several albatross species have been reported from Southern Ocean breeding sites (Weimerskirch & Jouventin, 1987; Gales, 1993; Weimerskirch et al., 1997) and have been linked to the high mortality rates caused by longlining operations (Croxall & Prince, 1990; Brothers, 1991; Murray et al., 1993). Most mortality has been associated with tuna fisheries (Bartle, 1990; Brothers, 1991; Vaske, 1991; Murray et al., 1993) and Patagonian toothfish Dissostichus eleginoides fisheries (Dalziell & de Poorter, 1993; Ashford et al., 1995; Cherel et al., 1996); little is known about seabird mortality from other longline fisheries. In South Africa, an experimental longline fishery was initiated in 1994 to exploit hake, Merluccius capensis and M. paradoxus, occupying rocky-bottom waters where trawlers are ineffective. This study reports the impact of the new fishery on procellariiform seabirds in the region. The study had two objectives: (1) to quantify the species, number and sex of seabirds being killed by hake longline vessels in South Africa each year; and (2) to assess the factors which account for the variance in seabird bycatch (both within and between vessels), and thus propose measures to reduce seabird mortality in the South African longline hake fishery. Factors suggested to influence seabird bycatch rates include: the time at which shooting occurs (Brothers, 1991; Murray et al., 1993), longline sinking rate (Brothers, 1991; Brothers et al., 1995), the intensity of moonlight if shooting at night (Vaske, 1991; Imber, 1994), weather conditions (Bartle, 1991; Brothers, 1991; Vaske, 1991), and temporal and geographical variation (Murray et al., 1993).

Keywords: Longline fishing, bycatch, seabirds, whitechinned petrels, Procellaria.

DESCRIPTION OF FISHING TECHNIQUE

*To whom correspondence should be addressed at present address: Avian Demography Unit, Department of Statistical Sciences, University of Cape Town, Rondebosch 7700, South Africa.

The South African experimental hake longline fishery was initiated in 1994, and after a period of monitoring 227

K. N. Barnes, P. G. Ryan, C. Boix-Hinzen

228

was upgraded to a commercial fishery in 1996. The fishery uses a Demersal Bottom Double Longline, a technique developed to cope with the rough grounds, harsh weather and strong currents characteristic of the South African fishing grounds (Japp, 1993a,b). Each line carries up to 15 000 hooks 1-5-2.0m apart, resulting in lines of up to 30 km long (Japp, 1993a). The longline has anchor lines with floats at either end and two continuous lines set on the bottom. The top line, the lighter, but thicker of these two lines, is buoyant and attached to the bottom line at 50--60 m intervals. The bottom line sinks and has the hooks, weights and floats attached (Japp, 1993b). Size 5-7 hooks, with a maximum length of 70 mm, are used for the hake fishery. They are baited with 70-120g chunks of thawed horse-mackerel Trachurus trachurus or pilchard Sardinops sagax. A longline of this type is directed at bottom fish. It has few floats attached and lies along the seabed, weighted at intervals (Japp, 1993b). Hake migrate vertically, occurring on or just above the seabed during the day and moving up through the water column at night. In order to target hake the gear is set after midnight to catch fish returning to the seabed in the early morning (Japp, 1993a). Lines are left in the water for up to 12 h prior to hauling. Fish are processed during hauling, which can take up to 8 h, and offal is ejected into the ocean. The hooks are then rebaited and the line redeployed.

METHODS Data sources and data collection

Observations on seabird-fishery interactions were made during three 4-day fishing trips, on three separate vessels,

25"S

i

between October and December 1994. Two larger boats, the Southern Fisher (38 m) and Aries (30 m) were stationed in Cape Town and fished the Agulhas Bank between Cape Point and Cape Agulhas (Fig. 1). A smaller vessel, the Barbara W (15 m) docked in Mossel Bay and fished over the Agulhas Bank east of Cape Agulhas (Fig. 1). The relative abundance of bird species in the immediate vicinity of the boat was estimated every 30min by counting all the birds passing a designated point within 20 m of the boat in a 30 s interval. Counts were conducted both during day and night, using the vessels' decklights to see birds flying at night. Six species and species groups were recognized (based on their relative abundance): (1) great shearwaters Puffinus gravis; (2) white-chinned petrels Procellaria aequinoctialis; (3) sooty shearwaters Puffinus griseus; (4) albatrosses Diomedea spp.; (5) pintado petrels Daption capense, and (6) other species, including gulls, skuas, terns and other shearwaters or petrels. The absolute numbers of white-chinned petrels attending the Aries and the Barbara W were counted every 30 min. These counts relied on sufficient natural light to see birds, and thus spanned c. 18 h of each day. An activity score of the first 10 white-chinned petrels seen attending the Aries between the hours of 2400 and 0600 was recorded every 30 min for three successive nights. The activity categories included: (0) a non-active bird (sitting), (1) swimming, (2) swimming and diving, (3) flying, (4) flying and foraging, (5) diving and competing for food. The activity scores of the ten birds were summed, resulting in an overall activity score ranging between 0 and 50. Thirteen hours of observation were devoted to watching the hauling procedure. Seabirds killed or

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Fig. 1. The study area, showing the ports used by hake longline vessels in South Africa.

Impact o f hake longline fishery injured during the hauling procedure were counted. Carcasses of birds which had been drowned during setting were collected. Participants in the experimental South African hake longline fishery were required to keep records of fishing effort, environmental conditions and catch rate. Key fishery variables recorded include: trip dates; numbers of hooks and floats; h o o k size, type and spacing; time when shooting commenced, and when hauling began and ended; the position at the start and end of each set; water depth; wind and current strength and direction; level of cloud cover; and sea state. The numbers of birds caught also should have been recorded, but several captains failed to complete this entry and others m a y have under-recorded seabird bycatch, given the perception that this information is not relevant or could even be damaging to their operations. To overcome this problem, logbook data were used only from vessels where an independent observer confirmed the veracity of logbook bycatch records. L o g b o o k s from two longline vessels, the Aries and Southern Fisher, apparently reported seabird bycatch data accurately. D a t a for 103 and 16 fishing days were available for the two vessels, respectively. D a t a analysis

Birds caught on longlines were identified to species and dissected to determine sex. Total numbers of seabirds killed were extrapolated from bycatch rates (birds killed per 1000 hooks set) and fishing effort data. Bootstrapping was used to calculate 95% confidence limits for all extrapolated values. Differences in white-chinned petrel mean activity indices were tested using a K r u s k a l Wallis test and a multiple comparison test (Zar, 1984). The contributions of eight variables that could influence seabird mortality rates recorded in the Aries logb o o k were estimated using a stepwise multiple regression (Zar, 1984). Moonlight was scored on a scale from 1 to 15, where 1 represents a new moon, and 15 a full moon. Two weather variables were incorporated: wind strength (in knots) and cloud cover (percentage). A cyclic variable representing the day of the year was

229

included to account for seasonal variation. Because trends in longitude and latitude tend to be autocorrelated with respect to bird abundance (Abrams & Griffiths, 1981), we only used longitude to account for regional variation. Water depth also was included because the distributions of m a n y bird species appear to be influenced by this variable (Ryan & Moloney, 1988). The number of floats/1000 hooks fitted to the line was used as an index of longline floatability. The final variable was the time at which shooting began relative to local sunrise. There were insufficient accurate data to undertake this analysis for other vessels.

RESULTS Composition and estimated magnitude of seabird bycatch

A total of 39 seabirds caught on longline hooks was recovered by observers; all were white-chinned petrels. O f these, 21 were male, 12 were female, the sex of one bird was undetermined, and five birds had been dissected previously and could not be sexed. Despite an apparent male bias, the observed distribution was not significantly different from an expected 1:1 sex ratio Xz= 1.94, df = 1, NS). The monospecific seabird bycatch differed markedly from the composition of birds attending the vessels. During the day, great shearwaters were by far the most abundant species around longline vessels (in O c t o b e r December), followed by pintado and white-chinned petrels, and lesser numbers of sooty shearwaters, albatrosses and other species (Table 1). At night, pintado petrels were observed most frequently, followed by great shearwaters and white-chinned petrels (Table 1). Sooty shearwaters, albatrosses and other species were inactive at night. Bird catch rate differed considerably between vessels: during the 4-day cruises with observers, 28 birds were caught by the Aries (0.48 birds per 1000 hooks), eight by the Southern Fisher (0.22 birds per 1000 hooks), and none by the Barbara W. The lack of birds caught by the Barbara W precluded the validation of the vessel's

Table 1. The relative abundance of seabirds attending hake longline vessels off South Africa during October-December (based on 30 s counts of birds passing within 20 m of the ship)

Species

Shy albatross Diomedea cauta Black-browed albatross D. melanophyrs Yellow-nosed albatross D. chlororhynchos Northern giant petrel Macronectes halli Pintado petrel Daption capense White-chinned petrel Procellaria aequinoctialis Great shearwater Puffinus gravis Sooty shearwater P. griseus Subantarctic skua Catharacta antarctica Gulls Larus spp. Terns Sterna spp.

Daytime counts

Night-time counts

Mean

SD

Range

Mean

SD

Range

0-41 0-82 0.09 0.04 4-18 3.73 21.36 0.64 0-23 0-09 0.09

00.65 0.72 0.29 0-21 4.11 1.76 6-04 0-98 0.60 0.42 0-42

0-2 0-2 0-1 0-1 1-17 1-7 12-32 0-4 0-2 0-2 0-2

-0.07 --3.93 2.78 3-36 0.14 ----

-0-26 --1.44 1.37 1.59 0.35 ----

-0-1 --2-7 1-6 1-6 0-1 ----

K. N. Barnes, P. G. Ryan, C. Boix-Hinzen

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logbook for seabird bycatch records. According to the other vessels' logbooks, the Aries caught 649 birds during 103 fishing days (Fig. 2), when 1 491 000 hooks were set (average 14475 hooks per day), at an average catch rate of 0.44+0.34 birds per I000 hooks (6-3 birds per day). The Southern Fisher caught 78 birds during 16 fishing days (Fig. 2), when 146000 hooks were set (average 9125 hooks per day), at a catch rate of 0.53 + 0-72 birds per 1000 hooks (4.9 birds per day). The variance between vessels complicates estimations of the impact of the entire fishery, but using the overall average catch rate (0.44±0.35 birds per 1000 hooks) gives an estimated 8000 4-6400 white-chinned petrels killed annually. Nine great shearwaters and two pintado petrels were killed during 13 h of hauling operations. Birds were either snagged by the longline as it was being hauled aboard (n = 5), gaffed by fishermen trying to retrieve fish (n = 2), or hit by a rubber dinghy which is also used to retrieve fish (n=4). Most of the birds killed during hauling were on the Aries, where offal outlets discharge waste adjacent to where the longline is hauled. Birds that gathered to feed on the offal were foul-hooked and dragged through the processor where the hook was wrenched out, invariably snapping the wing or limb it was attached to. Birds were then cast over the side to die. Based on these limited observations, hauling operations probably kill at least 1000 birds annually. Factors influencing catch rate

Only two of the nine variables were important in explaining the variation in the catch rate: time of shooting explained most (51%) of the variation (t = 9-8, partial coefficient = 0-193, p < 0.001), with m o o n state adding an additional 14% explanatory power to the model (t = 6-5, partial coefficient = 0-03, p < 0-001). The

final model was highly significant, explaining 65% of the variance in the data (Durbin Watson = 1-98, df = 100, p < 0-001). In general, later sets caught more birds. White-chinned petrels showed consistent changes in activity patterns between midnight and 0600 (Fig. 3; Kruskal-Wallis, p < 0.001). Prior to 0300 activity was static and low; between 0300 and 0330 activity levels increase dramatically and after 0330 activity levels climb steadily until sunrise just before 0600 (Fig. 3). The marked increase in white-chinned petrel activity occurs c. 2.5 h prior to sunrise. Longline shooting commenced between 0200 and 0330 during the observation period, suggesting that white-chinned petrel activity was largely independent of shooting. On day 1 the white-chinned petrels were already highly active prior to the start of shooting at 0330 (Fig. 3), whereas on day 3, when the line was shot at 0200, the birds remained inactive during the first hour of shooting. The variance in bycatch rate between vessels may be related to differences in the attractiveness of the vessels to birds in terms of food availability. The numbers of seabirds attending the Barbara W remained fairly constant over time, whereas the Aries attracted increasing numbers of birds throughout the 4-day cruise (Fig. 4 ). Fish processing aboard the Aries provides a continuous flow of offal for up to 13 h a day. Shortly after processing ceases, the longline is reset, providing food in the form of bait. Consequently birds are attracted throughout the day. By comparison, the smaller Barbara W only discards offal for short periods and in small quantities. Birds gather during fish processing, but then disperse and few are following the vessel when the longline is reset.

DISCUSSION 25

I 20-1

QAries [ [] Southern Fisher ]

~

15Frequency 10-

0

5

10

15

20

25

Number of birds killed per set Fig. 2. Frequency distribution of the number of birds reported killed each longline set by two vessels in the experimental hake fishery off South Africa (data from skippers' logbooks). Frequencies from the two vessels have been combined.

The average bycatch rate of seabirds by the South African hake longline fishery is similar to catch rates reported from other longline fisheries in the southern hemisphere, with the notable exception of tuna fisheries off the east coast of South America, where catch rates are an order of magnitude higher (Table 2). Quite why bird catch rates off South America are exceptional is unclear. What is of concern for the South African hake fishery is that the bycatch rate is relatively high, given that all setting takes place at night, and thus other control measures need to be instigated. The predominance of white-chinned petrels is similar to that reported in several other longline fisheries (Vaske, 1991; Ashford et al., 1995; Cherel et al., 1996). This species is strongly associated with fishing vessels off South Africa at least during winter (Ryan & Moloney, 1988), and fish wastes make up a substantial proportion of the diet (Jackson, 1988). White-chinned petrels feed primarily by surface seizing, but they are also proficient divers, regularly pursuing prey to depths of 6 m (Harper

231

Impact o f hake longline fishery

taking place at night, when albatrosses seldom feed (Bartle, 1974; Weimerskirch & Wilson, 1992). Vaske (1991) attributed the preponderance of whitechinned petrels killed by longline vessels off southern Brazil to their being the most numerous bird at fishing

et al., 1985; Harper, 1987; Huin, 1994), which enables

them to retrieve baited hooks for some distance behind the vessels. Albatrosses frequently are caught by other longline fisheries (Brothers, 1991); their absence from the hake fishery bycatch can be attributed to setting 50 ~dayl ---.--- day 2 ----~--- day3

40

Activity index

30 20 10 2,~.,.~,,, N~,~,e~oo0

2400

-..--

I

I

I

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0100

0200

0300

0400

0500

0600

Time of day Fig. 3. Indices of white-chinned petrel activity from midnight to 0600 on three consecutive days, 23-25 October 1994, around the longline vessel Aries. Local sunrise was at 05.55, and a waning moon (4-6 days after full moon) was above the horizon throughout the observation period. Day 1

40

Day 2

Day 3

Day 4

30Numbers of birds

20. 10. 0

. ~

0

~

~

12

Barbara W

24

36

48

60

72

84

Time (hours) Fig. 4. Numbers of white-chinned petrels following two longline vessels, the Aries and Barbara IV, over 4-day fishing trips. Table 2. Comparative seabird byeatch rates (numbers of birds caught per 1000 hooks) in Iongline fisheries

Region

Target fish

Tasmania, Australia New Zealand

Southern Brazil and Uruguay

Tuna Thunnus maccoyii Tuna Thunnus maccoyii (no control measures) (night swetting, streamer lines) Tuna Thunnus maccoyii

Kerguelen

Patagonian toothfish

South Georgia and adjacent areas

Patagonian toothfish

Dissostichus eleginoides Dissostichus eleginoides

South Africa

Hake Merluccius spp.

Bycatch rate 0.41 0.27 0.24 0.02 3.82 5.03 0.49 (0.15-1.00) a 0-67 0-47 0-28 (0-11-0.46) ~ 0-44

aRange of values, depending on time of setting and amount of deck lighting.

Source Brothers (1991) Imber (1994) Murray et al. (1993) Murray et al. (1993) Vaske (1991) Barea et al. (1994) Cherel et al. (1996) Dalziell and de Poorter (1993) Ashford et al. (1995) CCAMLR, 1995 This study

232

K. N. Barnes, P. G. R y a n , C. B o i x - H i n z e n

vessels. In this study, both pintado petrels and great shearwaters were more abundant, but only white-chinned petrels were caught during setting. Pintado petrels are known to dive and retrieve sinking bait, bringing it to the surface (Vaske, 1991; Imber, 1994), and great shearwaters are proficient pursuit divers (Marchant & Higgins, 1990). However, it may be difficult for these smaller species to swallow the baited hooks whole; instead they tend to peck at the bait dislodging it from the hook (Imber, 1994). Night setting has been shown to reduce dramatically the number of seabirds caught on longline hooks (Brothers, 1991; Murray et al., 1993; Ashford et al., 1995; Cherel et al., 1996). Murray et al. (1993) suggested that all sets should take place in darkness, ending at least 2h before dawn. However, Ashford et al. (1995) noted that although night setting would dramatically reduce albatross deaths around South Georgia, it would not reduce white-chinned petrel mortalities. A similar problem faces the South African longline fishery. Setting at night is better than during the day, but is not enough. If night-time setting becomes a standard measure to reduce bird bycatch, the pressure will shift from albatrosses to smaller nocturnal foraging petrels and shearwaters. Other measures are required to reduce the levels of mortality amongst procellariiforms that are active at night.

Factors affecting bycatch rate Time of shooting the longline explained most of the variation in white-chinned petrel catch rate. Later starts increase the chance of shooting extending into predawn or daylight hours, and thus catching more birds. It is well documented that more birds are caught during the day than at night (Brothers, 1991; Murray et al., 1993; Ashford et al., 1995; Cherel et al., 1996). Light intensity appears to be a more important cue than is longline shooting for triggering predawn activity of white-chinned petrels. Our observations confirm that moonlight increases seabird catch rate (Vaske, 1991; Murray et al., 1993; Cherel et al., 1996; Imber, 1994). Bright deck lights also increase the number of seabirds that are killed during night setting operations (Cherel et al., 1996). Lighting on the Aries and Southern Fisher exceeded that necessary for efficient and safe operation during setting. Experimenting with lighting may be one of the most effective methods of reducing unnecessary seabird bycatch at night. The variance between vessels in observed catch rate appears to be related, at least in part, to the extent to which birds accumulate around vessels. This, in turn, is a function of the length of time that offal is discarded. Smaller vessels are not as attractive to scavenging seabirds as are larger vessels which provide a continuous supply of food. If larger vessels were replaced by smaller vessels harvesting the same catch, this could reduce seabird mortalities.

Population impacts White-chinned petrels have only recently become a species for concern. Only 10 white-chinned petrels were recorded killed by tuna longlines in New Zealand waters, in part because the hooks used are too large for white-chinned petrels to swallow (Bartle, 1990; Imber, 1994). Low catch rates were reported also from Australia (Brothers, 1991). However, in addition to the estimated 8000 white-chinned petrels killed annually by hake longlining off South Africa, large numbers are killed by tuna longliners off Brazil (90% of birds killed, c. 2400 birds per year; Vaske, 1991) and by Patagonian toothfish longliners off Kerguelen (95% of birds killed; Cherel et al., 1996) and South Georgia (c. 2300 birds per year; Dalziell & de Poorter, 1993). The rapid expansion of toothfish fisheries in the Southern Ocean (e.g. around the Prince Edward Islands) is likely to boost this mortality figure to > 20 000 birds per year. Little is known about the total population size of white-chinned petrels, but it is estimated to be in excess of two million breeding pairs (Marchant & Higgins, 1990). Thus the estimated fishery bycatch is < 1% of the total population. However, there is cause for concern about long term population stability (1) because procellariiform life-history strategy involves delayed maturity, low reproductive rate and high adult survival (Croxall et al., 1984; Berruti et al., 1985), so that an increase in the mortality rate of white-chinned petrels could have a significant impact; (2) because fishing mortality is unlikely to be spread evenly across the population, with some colonies experiencing greater mortality than others; and (3) because of the rapid increase in longline fisheries within the range of the white-chinned petrel. Long-term monitoring of breeding colonies is required to assess the extent of longline mortality on the demography of this species (Ashford et al., 1995). Recommendations to reduce seabird bycatch The most important way to reduce seabird bycatch is to set longlines in the middle of the night, using the minimum of deck lighting. Setting should be completed at least 3 h before sunrise, prior to the increase in whitechinned petrel activity. Bird (or tori) lines are known to be highly effective in reducing seabird bycatch by longline fisheries (Brothers, 1991; Murray et al., 1993), including white-chinned petrels feeding at night (Ashford et al., 1995). Given the large numbers of birds caught by the hake longline fishery off South Africa, use of bird lines should be mandatory. In the absence of measured sinking rates of the longlines, we could not assess accurately the importance of this factor in explaining bird catch rates. However, lines designed to bottom-set, such as those used in the South African hake fishery, can be weighted to sink quickly, which could further reduce seabird bycatch. Mortalities caused by gaffing, collisions with dinghies, and injuries from hooking on the longline during hauling

I m p a c t o f hake longline f i s h e r y

are not reported as bycatch and go unrecorded. It is important that these additional sources of mortality be quantified. Great shearwaters, the primary victims of this hauling mortality during the study period, occur in South African waters as passage migrants (Ryan & Rose, 1989). At other times of the year, the species composition and rates of hauling mortality may be different to those recorded on the Aries in mid-October. Mortality during hauling operations can be avoided by dumping offal only on the opposite side of the boat to hauling operations (Brothers, 1994). Another option is to place restrictions on the timing and extent of offal dumping. Fishermen need to be educated as to the benefits of not catching birds. In Australia, white-chinned petrels have been observed to remove bait from a large proportion of hooks, disrupting fishing operations (Brothers, 1994). Similarly, hooked birds tend to buoy up the longline, removing adjacent areas of the line from the desired fishing depth. These impacts substantially reduce fishery profits (Brothers, 1991, 1994). Once fishermen are aware of this financial incentive, it should be possible to implement mitigation measures in the South African hake longline fishery to the benefit of both the fishery and pelagic seabirds.

ACKNOWLEDGEMENTS Dave Japp and Jan Wissema, Sea Fisheries Research Institute, arranged trips on the longline vessels and provided access to fishery records and literature. We are grateful to the skippers and crew members of the Aries, Southern Fisher and Barbara W for their co-operation. John Cooper provided useful comments on an earlier draft of this paper. Financial support was received from the South African Foundation for Research Development, the University of Cape Town's Research Committee and the World Wide Fund for Nature, South Africa.

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