1. PARTICIPANTS NCMR (Responsible Institute), IMBC [Greece] IREPA[Italy] U. Barcelona, U. Basque, UPO[Spain] EFIMAS MEETING NICOSIA CRETE 2004 APRIL 11-12

2. Fishery Overview The European hake, Merluccius merluccius L., 1758, is a gadoid species distributed the commercially most important demersal species in the Mediterranean Sea. It is fished with throughout the Mediterranean Sea, occurring at depths from shallow waters to 1000m. It ranks among trawl nets, bottom longlines and fixed-nets. Hake fisheries are of the major Mediterranean fishery in terms of output quantities, value and management options and there is considerable biological information. Economic information on this fishery is also very good e.g. costs of fishing prices, investments, subsidies, incentives and so on.

3. Possible elements contained in the two types of data Biological data

4. Assessment methods The methods currently employed to assess the state of exploitation of the hake stocks in the Mediterranean are:  Until 1980, the Shaefer and Fox production models were applied to those hake stocks for which historical series of catch and effort data existed.  After 1980, yield-per-recruit analysis (Y/R) was applied in certain areas. This analysis demonstrates overexploitation of hake and a high level of current fishing mortality.  More recently, virtual population analysis (VPA) or length cohort analysis (LCA) has been applied by Martin (1989), for some stocks, mainly off the Spanish coast, but also in the Gulf of Lions where hake is exploited by a multigear fishery (Aldebert & Carries, 1991), and Aegean Sea (Papaconstantinou et al, 1992). High levels of fishing mortality were recorded in all cases. Subsequent Y/R analysis indicated overexploitation.

5. Management measures §The common management measures applied in fisheries targeting hake in the Mediterranean are the following: l introduction of a minimum mesh size in the trawl fishery, l limitations in the minimum size of marketed fish, l implementation of closed inshore areas and/or seasons, l restriction on the number of licences issued, and l restrictions on the fishing effort. Apart from certain technical measures (e.g. minimum landing size) there is lack of harmonized measures among the different Mediterranean countries.

6. Management problems §Application of single species models in a multi-species fishery §Multi-gear fishery §Discards of juveniles §Overlapping of nursery and feeding grounds §Age determination (1 st year) §Stock definition

7. Main typological problems to address  Ban of trawling over the continental shelf during the recruitment period.  Implementation of a mesh-size in trawl nets larger than 40mm.  Restrictions to the fishing effort (time spent at sea, control of engine power).

8. Partnership input Mediterranean Hake Fishery Case Study Specific inputGeneric input Biologica l Economical/Sociol ogical Biologica l Economical/Sociolog ical NCMR, IMBC, IREPA IREPA, NCMR, IMBC NCMR, IMBC, IREPA, UPO, Univ. of Basque Country, University of Barcelona

10. General concepts of a fisheries model Relationship between fish stock assessment, management objectives, strategies and regulations (from King 1995, modified)

11. Catch/effort of total commercial catch.  Length or age-frequency data from commercial fisheries or research surveys.  Biological data (maturity stage, length/weight etc) from research surveys and/or from sampling commercial fisheries.  General knowledge of the biology of species (spawning season, migration, etc.) and of the fisheries (area, gear, season).  Estimation of growth parameters.  Catch curve analysis.  Virtual population or cohort analyses.  Surplus production models.  Swept area method (research surveys) Von Bertalanffy growth parameters.  Length-weight relationship.  Total mortality.  Fishing and natural mortality.  Exploitation rate  Stock size (size composition of stock). Beverton and Holt’s yield per recruit model.  Thomson and Bell’s model (for single stock or mixed fisheries).  Surplus production models.  Swept area method combined with a Gulland-type of model OPTIMUM FISHING LEVEL (The optimum level of fishing mortality) MAXIMUM SUSTAINABLE YIELD OR VALUE and present position with respect to optima Analyses of historical data Estimates of population parameters Fisheries data (+assumptions) Predictions of yield INPUT PROCESS INTERMEDIATE OUTPUT PROCESS FINAL OUTPUT General flow chart for fish stock assessment * (*) based mainly on Sparre, P.; Venema, S.C.. Introduction to tropical fish stock assessment. Part 1. Manual. FAO Fisheries Technical Paper. No. 306.1, Rev. 2. Rome, FAO. 1998. 407p.