4) Observation. It is harder to see catch-efficiency im- 

 provements when compared with seeing marketable fish es- 

 caping through the meshes when the net is at the surface. 



Application of Mesh Management 



Deciding to use mesh size regulation as a management tool is 

 only the first step on a long road towards successful applica- 

 tion. The second, and probably the most important, step is to 

 determine what goals are to be attained by mesh size regula- 

 tion. The most obvious role mesh size can play is in the reduc- 

 tion of discards of undersized fish. The problem here is to 

 define what an undersized fish is. To a fisherman it may be any 

 fish too small to market profitably, or legally, if there is a 

 minimum size regulation enforced. To a scientist or manager it 

 may be any fish smaller than some optimized size based on 

 yield or yield per recruit. 



Generally, discards of undersized fish decrease with increas- 

 ing mesh size. At a certain point, under steady state condi- 

 tions, a mesh size that would maximize the yield from the 

 fishery, in weight, will be reached. The key variables that af- 

 fect this point are fishing mortality, natural mortality, and 

 growth rate. A mesh size can be chosen to attain this goal. 

 Mesh size can also be chosen to protect a certain portion of the 

 spawning stock, i.e., allow the fish to reach a size to spawn at 

 least once or twice before recruiting to the fishery. The size 

 mesh needed to accomplish this usually lies between that 

 necessary to reduce discards of fish too small to market and 

 that needed to maximize the yield of the fishery by weight. 

 There may also be an economically optimum mesh size, one 

 that would provide a supply of certain size fish that would 

 maximize the return to the fishermen or stabilize prices. 



Mesh size may even be used to limit effort over the short 

 term. Increasing the mesh size by an increment that would off- 

 set any catch increases due to improved efficiency would cause 

 a decrease in catch per unit effort. However, a new steady state 

 condition will eventually be reached where CPUE may be 

 greater than before or the fishery would be beyond the op- 

 timum point of harvesting. Assume that a mesh size is chosen 

 that is a compromise between reducing discards of un- 

 marketable fish and optimizing the overall yield (weight land- 

 ed) of the fishery and in so doing protects the first spawners. 

 Assume also, for now, that it is a single species fishery that is 

 being discussed. The next step is implementation of the mesh 

 regulation and, correspondingly, the enforcement of it. 



It has been argued that if fishermen are fully informed and 

 believe in the benefits that would accrue to the fishery there 

 would be no implementation problems. However, the benefits 

 accrue to the fishery, not necessarily to an individual fisher- 

 man. It is easier for a fisherman to see marketable fish escap- 

 ing his large mesh cod end than to see gradual long-term in- 

 creases in catch for the industry. Better prospects in the fishery 

 may encourage more entries and an individual's share might 

 not change at all. Whatever the reason, there is an incentive 

 for fishermen to look at short-term losses rather than long- 

 term gains. This incentive is highest when recruitment is 

 strong. 



The simplest way to avoid the regulation is to fish an under- 

 sized cod end and hope not to get caught. If the fisherman 

 does get caught, the penalty, if any, is usually insignificant 

 compared with the gains made by cheating. If a fisherman 

 wants to decrease his chances of getting caught, he can fish a 



small mesh liner inside the regulation cod end. This allows him 

 to remove it before entering port or upon the arrival of a Coast 

 Guard vessel. There is also the technical loop-hole. For exam- 

 ple, if the regulation does not specify the length of the cod end 

 required, the fishermen could attach an extra short cod end of 

 regulation mesh to an extension piece of smaller mesh size. A 

 way to avoid this may be in using more general definitions such 

 as defining cod end as the "terminal portion of a trawl in 

 which the catch is normally retained." There can also be the 

 honest mistake of a fisherman using a nonregulation mesh 

 because he was sold the wrong size. 



In a single species fishery the above problems should be 

 relatively easy to solve. To counter the incentive to cheat, a 

 greater disincentive must be present. Fishermen in New 

 England suggest vessel "tie-ups" for those that violate the 

 regulations. Some fishermen believe repeated violations 

 should lead to suspension and even loss of license to fish. To 

 aid in clear-cut identification of violators, the regula- 

 tions must be black and white; no gray areas. One rule, for ex- 

 ample, could be that a vessel may only have one mesh size on- 

 board even to the point of requiring all parts of the trawl be at 

 least the same mesh as the cod end. 



To eliminate problems of what constitutes a legal cod end, a 

 certification program may be in order. Such a program existed 

 in New England during the 1950's on a voluntary basis. 

 Fisheries enforcement agents were contacted by a dealer when 

 a shipment of new cod ends arrived. The agents would go to 

 the dealer and certify the cod ends by measuring and compar- 

 ing with a set of standards that took into account material type 

 and shrinkage rates. Upon passing, the cod end had four 

 numbered brass tags squeezed onto it and then soldered. The 

 cod end was then considered certified legal unless major (10%) 

 repairs were undertaken. The system worked fairly well until 

 the number of variations in twine type and quality became ex- 

 cessive and many failed to meet government specifications. At 

 this point cod end manufacturers guaranteed their cod ends to 

 the fishermen as legal size or they would stand the conse- 

 quences. Eventually the voluntary certification program was 

 phased out. Today, however, there seems to be a need for a 

 certification program, quite possibly with a less rigorous set of 

 criteria. Too many cod ends are being sold as legal size when 

 they are not even close, even before shrinkage. 



Another solution that is commonly advanced is the use of 

 minimum size limits. A minimum size limit serves two main 

 purposes. First it encourages fishermen to use the regulation 

 mesh and, secondly, it discourages fishermen from fishing on 

 populations of predominantly small fish. The problem with 

 size limits is how to set them in relation to the 50% retention 

 point of the regulation mesh. If the size limit is set lower than 

 the 50% point, the fishermen have incentive to cheat as legal 

 size fish are escaping the regulation mesh. If the size limit is set 

 too high in relation to the 50% point there would be high 

 discard rates nullifying the benefits of the regulation mesh. 

 Setting the minimum size limit to correspond with the 50% 

 retention point is a poor compromise at best. What may be a 

 better approach to the problem is to set the size limit on a pro- 

 portional basis closely corresponding with the selection curve 

 of the regulation mesh, e.g., no more than 20% of the cod 

 and/or haddock landings of a trip can be scrod (by weight). 

 This sort of system would require better accountability at 

 wharfside. One way to do this is to require all boxes of fish to 

 be labeled (vessel, trip number, market category, and serial 



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