2. DESCRIPTION OF THE FISHERY

2.1 The resources
2.2 The fleets

2.1 The resources

By the tonnage caught (about 200 000 tons annually) and its commercial value, the cephalopod fishery in the northern part of CECAF represents one of the most important in the region as well as in the world. The species which mainly contribute to the catches are the following:

- octopus:	Octopus vulgaris
- cuttlefishes:	Sepia officinalis var. officinalis
	S. officinalis var. hierredda
	S. bertheloti
- squids:	Loligo vulgaris
	L. forbesi

Among the cuttlefishes, S. officinalis officinalis is distributed in the northern part of the fishing area down to 16° latitude N approximately (see figure 2). It is progressively replaced by S. officinalis hierredda. the abundance of which begins to be noticeable south of 21° latitude N (see Appendix 4). The third species is of lesser importance (some 5% of the overall cuttlefish catches).

Loligo vulgaris predominates among the squid species. L. forbesi is noticeably less abundant and its area of distribution does not extend further south than 23-24° latitude N.

Although octopus, cuttlefishes and squids occur at all latitudes in the northern sector of CECAF, specialized fisheries only exist so far between 26° and 13° latitude N approximately (figures 1 to 3, table 1-resources). The exploitation initially started in the northern part of that sector from which it progressively spreads to the south. Actually, the exploitation of grounds south of Cape Verde only started a few years ago and a further southwards expansion of the fishery is not to be excluded, but occurrence north of 26°N of concentrations of appreciable commercial importance is less likely.

Fishing operations are to a large extent concentrated within four major grounds (figures 1 to 3). Although the various species categories can be caught in commercial quantities everywhere between the boundaries drawn on these maps and even if appreciable differences are noted in the limits of the fishing grounds corresponding to each species group, the bulk of the catches comes from four main sectors:

- Cape Garnett - Cape Barbas (22°30' - 26°00')
- Cape Blanc
- Nouakchott
- Cape Verde (south)

The identity and distribution of stocks are poorly known. Exchanges between the various fishing grounds are probably very limited for octopus which are poor swimmers. They can be expected to be somewhat higher for cuttlefishes and especially for squids which have better swimming capabilities. No appreciable migrations in latitude between the various fishing grounds or displacements of the fishing grounds themselves have been observed. This does not mean that such movements do not occur for the most mobile species, e.g. squids. Limited depth migrations have been noted. For instance, the juveniles of octopus and cuttlefishes are more abundant in inshore waters. If the latter species move inshore for spawning, no similar displacements have been recorded for octopuses, contrarily to what has been observed in other regions.

However, for the time being, separate assessments by fishing grounds are largely impossible. If Japan collects fishery statistics by 30' statistical squares and if Spain has until 1977 been essentially fishing within the northernmost ground, no data broken down by fishing grounds are available from the other countries.

On the various grounds, certain species are exploited all the year round; others are more available at certain seasons (see tables 1 to 3). The reasons of the existence or absence of such seasonal variations are not fully clear. The vulnerability of certain species (octopus, squids, for instance) may change with seasons, the former being less vulnerable daring the spawning season when females remain in shelters, the latter being more accessible as adults gather for spawning. The weather conditions also affect the fishing efficiency. Finally, the biomass - and therefore the catch rates - are affected by the timing of recruitment.

2.2 The fleets

Spain, followed by Japan, was the first country to enter into the fishery. In recent years, the number of larger vessels from Japan has notably decreased, although the number of vessels of smaller size has remained more stable. To a certain extent, the decline of Japanese operations has been compensated by an expansion of the activity of Korean trawlers. As noted above, the fishery south of Cape Verde started to develop only recently. In that sector, most of the catches are made by Senegalese canoes; they are subsequently transhipped or processed ashore. Participation of other countries in the cephalopod fisheries is of secondary importance.

The main data available on the present characteristics of the fleets (size and number of boats, distribution of national fishing operations, mesh sizes used, etc.) are summarized in table 1 - fleets.

In these fisheries for cephalopods, several species of finfishes are simultaneously caught in varying quantities. If the most valuable species are kept, appreciable amounts are also discarded^1/. By-catches are likely to generate difficulties in the assessment and management of the simultaneously caught species and its consequences for mesh size regulation have already been noted for the Hake, sea breams and cephalopod fisheries (see section 3.3). Among the main species caught as by-catches in the cephalopod fishery, the following should be mentioned:

^1/ Bravo de Laguna, G., M.A.R. 1976 Fernandez and J.C. Santana, Discardings of fishes in the cephalopod fishery off West Africa - ICES Shellfish and Benthos Committee, Demersal Fish (Southern) Committee, CM 1976/K:32 (mimeo)

Bravo de Laguna, G., M.A.R., 1977 Discarding of sparids in the bottom trawl fishery off Northwest Africa -ICES Demersal Fish (Southern) Committee, CM 1977/G:12 (mimeo)

Bravo de Laguna, G., M.A.R., 1977 Length distribution of the fishes discarded in the bottom trawl fishery off N.W. Africa - ICES Demersal Fish (Southern) Committee, CM 1977/G:13 (mimeo)