Experience of the application of mesh regulations in other areas has shown that when such regulations are introduced and begin to be enforced, practical difficulties can arise in respect of certain groups of vessels. These difficulties can be of two types. First, there are the vessels to which the regulations are applied but which find that, because of the nature of their catches (especially of species other than those for Which the mesh regulation is intended), the use of large, legal-sized meshes cause unacceptable drops in catch. Secondly are those vessels to which the regulations do not apply, but which still catch sufficient numbers of small fish of the species of interest to reduce significantly the benefits from the regulations.
These problems, particularly of the first type, were considered by the CECAF Sub-Committee, and paragraph 2 of its recommendation (see above) was framed in order to minimize possible difficulties. However, the practical implementation of the regulations may bring out some difficulties not considered by the Sub-Committee. The likelihood of such difficulties, at least so far as the hake fisheries are concerned, can be judged from the information presented by the Ad hoc Working Group on Hakes, by considering each major fishery for hakes.
The Spanish fishery is very largely for hakes; other species caught include sparids. It is clear that the mesh regulation should apply to these vessels, and that apart from a short-terra drop in catches they should have no difficulty as a result of using the larger meshes and will in the long term benefit considerably. At present these trawlers use meshes ranging from 40 mm up to 60 mm. An abrupt change from 40 mm up to 70 mm would probably cause a short-term loss (i.e., for perhaps the first year after the adoption of the 70 mm mesh) estimated by the ad hoc group to be about 25 percent. This may be larger than can be reasonably accepted by the fishermen. In that case a phased introduction may be necessary - perhaps immediately to 60 mm, and after two years, the introduction of 70 mm.
The Portuguese trawlers also catch a high proportion of hake. Their mesh size has recently been increased to 65 mm and a further increase to 70 mm would seem to involve no problems.
Hake make up only a small percentage, now about 5 percent, of the total trawl catch by the U.S.S.R., and on this basis the U.S.S.R. fleet would, under the terms of the CECAF recommendation, not be bound to use a 70 mm mesh size (their present mesh size is about 60 mm). However, their total catch of hake is very considerable - around 2/3 of the catches from the southern stocks - so that their exemption from the provision of the regulation would be highly undesirable. In practice the Soviet trawlers apparently use two types of trawl - one for bottom fish, and one for pelagic fish (sardines, etc.). It is probably that the percentage of hake when actually fishing with a bottom trawl is high, or at least above the 20 percent exception level. More information is needed on the operations of these vessels to determine how well fishing for demersal and pelagic species can be separated, and how a 70 mm mesh size in the former operations can be adequately enforced.
The Moroccan fisheries are likely to present the biggest problem since the meshes currently used appear to be very small - around 30-40 mm, while the catches of all classes of Moroccan vessels taken together make up a significant proportion of the total catch of M. merluccius in the CECAF region. The report of the Ad hoc Working Group does not contain information on the catches of species other than hake, and there may be differences in the composition between the catches of the larger (ca. 250-300 GRT) vessels and the smaller trawlers of around 50 GRT. It is possible that at least the latter group may catch a sufficient amount of small species as to make a 70 mm mesh difficult for them to adopt. In any case, an abrupt change from 30-40 mm up to 70 mm would, as for the Spanish vessels, cause great practical difficulties. A first step, up to say 50-60 mm, would be more acceptable, and possibly also more consistent with the optimum mesh size for the other species being caught.
Further information is urgently needed in order to decide which mesh size would be best for the Moroccan trawlers to use and there might be a difference between the optimum mesh size for large and small trawlers. This information should include more data on the numbers and sizes of hake caught, and on the other species caught, including information on their sizes. This information should enable a balance to be struck between, on the one hand, losses to the hake fishery (including losses to the Moroccan vessels themselves) through the possible use of meshes smaller than 70 mm, and the possible changes in the catches of other species through the use of meshes larger than those currently in use. For the latter it should be noted than the changes need not necessarily be losses; the long-term catches of other species may well also benefit from the use of larger meshes.
