Fish catching methods of the world

176

great extent, although it is also exposed to chlorination (to control biofouling in the machines). Survival rates ranging from 48 to 98% were recorded, b u t when the water temperature exceeded 29°C, mortality was nearly 100%. To sum up, it may be concluded that although little effect from so-called "thermal pollution" has been recorded, this b o o k is a valuable monograph on the assessment of resources and on ecological and biological as well as hydrographical studies in this interesting area. It also gives valuable baseline studies for later investigations when more serious man-made changes may threaten marine life in the same or in similar areas. Such a monograph should also be very valuable for other areas threatened by environmental man-made problems, for instance parts of the North Sea. G. N A EV D A L

Department of Fisheries Biology University of Bergen Nordnesgt. 33 N-5000 Bergen Norway

FISH CATCHING METHODS

Fish Catching Methods o f the World by A. von Brandt. 3rd Edn. Fishing News Books, Farnham, 1984, 418 pp., 733 figs., 690 refs., £27.50, ISBN 0-85238-125-5. This must be regarded as the standard, general reference on fishing techniques used t h r o u g h o u t the world. It is a source of basic information on fishing gear and methods; the place to start in the field of fishing technology. It is descriptive rather than analytical, conceptual rather than detailed, comprehensive rather than specialized, narrative rather than mathematical. Its wide appeal is substantiated b y the appearance of this third edition, and each edition, revised and enlarged, has been twice the size of its predecessor. This exponential growth is the result of the author's wish to cover all fishcatching methods, not just those of contemporary commercial importance. The contents are ordered in a systematic and progressive w a y through 31 chapters, showing the evolution of fishing principles from the simple to the more complex and sophisticated. There is considerable cross-referencing within the text, relating various concepts to one another, and the three indexes (Subject, Species and Product, Geographical) make it easy to relocate ideas. For those wishing to pursue specific ideas in greater depth, there is a substantial bibliography o f 690 references in many different languages. The language of most non-English references is identified. This is not so for the German and French references, but in these cases, the title usually reveals the language. For readers whose first language is English

177 and who expect to find references by a n o n y m o u s authors to be listed under " A n o n . " , such references appear under " N . N . " for nescio n o m e n (name unknown). The book is n o t highly technical in the sense of an engineering report or scientific paper. Rather, it is a subjective description of fishing gears and methods, copiously illustrated (there are 733 figures), often interspersed with anecdotes and sometimes a bit wordy, which makes reading easier and often stimulates interest. History, principles and concepts are presented in a simple way, often discussing the " w h y s " and "wherefores" of various gear configurations and methods of use, but there is very little detail on " h o w t o " design, build and manipulate the gears. Because emphasis is on fishing principles rather than on commercial practice, considerable space is given to describing artisanal gears and methods. Thus, there is a wealth of ideas, derived from these unusual and little-used methods, which could provide inspiration in commercial innovation. Commercially important methods are described in principle, but exhaustive details are left to the plethora of other references, so that advancing technology should not make this reference obsolete. Occasionally the presentation becomes a bit awkward in relation to semantics or to satisfy an academic or theoretical consideration, but this should n o t bother the practical fisherman or fishing-gear technologist. Words such as "self-catching" on p. 9 to describe a factory ship which can catch as well as process its own fish and "air-plotting" on p. 33 for the process of plotting the position of fish shoals according to observations made from the air, add character to the book. Sometimes the context indicates t h a t the intended meaning is a little different from that of the word actually used. For example, on p. 41 the word "vertical" (which means perpendicular or normal to the plane of the horizon) is used to describe a fish which becomes perpendicular or normal to the electrical field, but which is more nearly horizontal (parallel to the plane of the horizon) than vertical. On p. 81 the work "remarkable" (which more often refers to exceptional, unusual or striking things) seems to be used simply to indicate t h a t the reader should take note. Another slip, often made by English authors also, is the spelling of "sheer" (e.g. pp. 111 and 112) with reference to the athwartwise h y d r o d y n a m i c force exerted by boards to cause supporting or towing lines to deviate from a direct downstream position. To shear is to cut as with scissors and, in mechanics, a shear force (as generated by scissors) causes successive layers of a material to be displaced in their own planes, but to sheer is to deviate from course, to swerve aside, and the sheer of a deck is the deviation of its fore-and-aft line vertically from straight to curved. Any shear forces in or on trawl doors bear little or no relation to their function of sheering the warps to either side from straight aft. The spreading force generated by the boards is derived from the displacement of a mass of water and is more a ploughing action than a shearing action. On p. 118 " t h e main part of a spoon w i t h o u t a

178 h a n d l e " could more simply be called its bowl. On p. 206 and elsewhere reference is made to fish fences made of twigs. However, a twig is a small shoot from the branch of a tree, such as would be used for starting a fire, and it is probable t h a t the fish fences are made of something more substantial, such as boughs or branches. On the same page the phrase "neutral c o n t r o l " probably refers to quality standards and testing by an agency not directly involved in the trade of fishing gear materials. In the caption of Fig. 434 (p. 226} the word "controlling" is used where the lines only feel or sense the presence of the fish but exert no influence or actual control over the behavior of the fish. On p. 387 it is probable that zoologists and physicists, rather t h a n physicians, became interested in fishing problems. Despite the excellent job of revising and enlarging this third edition, there are still a few places where the technology could be amplified or expanded to advantage. Perhaps this will always be so. In hook-and-line fishing, the presence of the pole n o t only takes the h o o k further from the scaring presence o f the fisherman, as stated on p. 83, but if appropriately constructed it also improves the action of the h o o k to secure the fish. In the " a u t o l i n e " system, the hooks are not removed from the mainline, as stated on p. 103, but are cleaned, untangled, controlled and stored in magazines with the mainline still attached, as shown in Fig. 166. Dark floats m a y be inconspicuous in the water, as indicated on p. 110, when viewed from above, but t h e y are very conspicuous when viewed from below in the daytime. Wooden traps are recognized on p. 179 as being heavy, but it should also be pointed out that t h e y must be weighted, as with stone ballast in the base, to prevent their floating off the seabed while fishing. To haul a pot line requires a lot of manpower, as stated on p. 192, but even so the effort or energy per pot is less than with pots set singly. Polypropylene (PP) should be included on p. 206 in the list of chemical fibres suitable for netting. In the comparison on p. 210 of various types of knotless netting with k n o t t e d netting, it should be pointed out t h a t for the same fibre, mesh size and bursting strength of individual meshes, a Raschel netting panel of the same area is heavier and the mesh bars thicker than is k n o t t e d netting. The absence of knots permits the knotless netting to fall in its own plane through the water more easily, giving advantage to hexagonalmesh netting in purse seines, but the thicker mesh bars present greater resistance to the flow o f water through the netting, which is a disadvantage in trawl-nets. The big advantage of knotless netting is that it is less prone to mark the fish, which is a factor when live fish are sought. The special purse-line block, for brailers as shown in Fig. 418 on p. 220, should be mentioned. This block permits the line to be hauled to close the brailer, it holds the brailer closed while the fish are brailed from the net and, with a tug on the line, it releases the line to permit the brailer to open and d u m p the load o f fish as required. Questioning the viability of combination trawler/ purse-seiners, as on p. 246, should also be extended to include the fishermen. Trawling and purse-seining each require different, highly-developed skills,

179

and captains and crew expert in b o t h are very rare. The discussion of Vdoors on p. 249 recognizes t h a t t h e y generate lower spreading forces than other types of doors of the same size. However, t h e y are inherently very stable, making t h e m easier to handle and retaining more of their spreading effectiveness under adverse conditions where more sophisticated and hydrodynamically efficient designs tend to collapse. The b u o y a n c y of trawl floats does n o t decrease with increase in towing speed, as claimed on p. 251. If a mid-water trawl is rigged to fish with its float-line at the same depth as the trawl doors, then a change in towing speed does n o t alter the height of the headline in relation to the doors; the lift of the floats remains constant. In a groundfish trawl, an increase in towing speed increases the drag force on the floats, forcing the headline back and down. The headline is lowered by increased downward force from the gear and not by any decrease in float b u o y a n c y . If the float is given a "sheering" shape, then the increase in its lift force with speed is h y d r o d y n a m i c rather than buoyant. In Fig. 500 on p. 260, the line marked " 8 " is n o t the warps. It is the electric cable which connects the electrical equipment on the headline of the net to the automatic slip-ring winch on the upper deck. The trawl warps are the two lighter lines shown aft from the stern rail. Also, the wireless netsonde does not transmit its signals through the water by radio, as claimed on p. 266. The signals are transmitted on an acoustic beam, not by electromagnetic radiation. The h y d r o d y n a m i c principles applied in the design of otter boards include camber, end-plates, paravane construction, etc., and not just high-aspect-ratio, as inferred on p. 267. Research and development to reduce the drag of mid-water trawls is aimed more at achieving larger trawls or higher towing speeds for larger catches with the same fishing effort than at conserving energy, as indicated on p. 270. In addition to using the towing power of the skiff to keep the seiner from drifting into the net while pursing, as described on p. 307, the seine is usually set so that the vessel is downwind of the net when the net is closed and tends to be blown clear. In Fig. 575 on p. 311, the stern ramp is probably more to permit the skiff to be hauled aboard for travelling than as a feature of net handling. The advent of the power block, as described on p. 312, permitted the seine to be stacked directly on the deck in a manner suitable for resetting. This eliminated the turn-table, which was otherwise required to redirect the stacked seine toward the stern for re-setting after it had been fleeted on board over the side or quarter. The position of the power block high on a boom may present stability problems in rough weather, but it gives the fish more o p p o r t u n i t y to slide down the netting into the b u n t for brailing rather than having to be removed from the net individually by hand. The harvester in Fig. 727 is n o t strong enough to be forced into the seabed, as claimed on p. 382; it digs its own way in with hydraulic jets. The Classification o f Catching Methods is a significant contribution to the field of fishing technology. Each time it appears it is slightly changed, and this refinement is likely to continue, probably with improved definitions

180

o f categories rather than changes in classification. For example, the essential differences between 5.2.2., 5.6.1 and 5.6.2 is not clear; t h e y are all fences for constraining fish. In 5.4, identifying tubular traps as "genuine" or " s m o o t h " hardly seems a valid distinction. The difference between 7.1.3 and 7.2 is n o t clear, particularly when Figs. 415 and 427a show essentially the same gear construction. The stated difference between 7.4.1 and 7.4.2 is not really illustrated b y Fig. 446; b o t h gears are shown anchored. Perhaps the intended difference relates to stakes vs. flotation being used to achieve vertical opening o f the net mouth. Again, the difference between 8.3.2 and 8.3.3 is not clear; surely the boat dredge in Fig. 459 is large enough to require mechanical handling and the mechanical dredges in Figs. 463-465 are fitted on boats. For category 9.2.2, Fig. 541 illustrates a beach seine (category 9.2.1), and perhaps this reference should be to Fig. 552. Also, in 9.2.2 differentiation should be made between anchor-dragging (Danish seining) and fly
P.J.G. C A R R O T H E R S

Department o f Fisheries and Oceans St. Andrews, N.B., Canada