D o no td is se m in at e w ith ou ta ut ho ICSR October 25 ra ut ho riz at io n Catch capacities of scallop fisheries in Brittany. Years 1945-25. Spyros.Fifas@ifremer.fr
ICSR October 25 Historical trends of scallop populations after the 2 nd World War. (1) Hydroclimatic component: Scallops may benefit because of temperature increase and of global warming. (2) Changes of coastal inshore fishing activities: From generalized motorization of vessels to computer processing on board. Continuous increase of catch capacities. 5 45 4 35 3 25 2 15 1 tonnes 5 Evolution of Scallop production 1915 192 1925 193 1935 194 1945 195 1955 196 1965 197 1975 198 1985 199 1995 2 s France G. Britain Favourable conjuction of both factors
ICSR October 25 annual mean T ( C) 15. 14. 13. 12. 11. 1. Increase of sea temperature (example of the Bay of Saint-Brieuc; VIIe). y = -6E-8x 4 +.5x 3-1.4236x 2 + 1857.8x - 98833 R 2 =.8466 19 1915 193 1945 196 1975 199 25 (i) Polynomial fitting for 2th century. -> Long term trend: warming mainly for four last decades. -> Mean term periodicity: cycle of 7.5 8 s (vs. sun energy?) -> Short term: seasonality. Fitting on s with number of daily measurements greater than 1
ICSR October 25 The Bay of Brest (period 1945-1963)....all areas of the Bay of Brest are taken over by Pecten beds spread in all small bays. Many scallops can often be caught in eelgrass fields of Saint Marc during spring tides (PRIOL, 193). The Bay of Brest and other scallop beds of South Brittany (e.g. Belle- Ile) had the highest densities before the Channel stocks (Saint-Brieuc, Seine) became larger. Period just after the Second world war: conjunction of a positive dynamic of the resource and by the evolution of catch capacities of the fleet (generalized motorization of vessels in 1953-1954). Collapse in 1963 (severe winter and recruitment over-fishing). Conversion of length composition of population (LE GALL, 1952; FAURE 1952, 1956, 1966) to age composition including individual growth variability -> Fishery dynamics of the first half of 5 s.
Bay of Brest: evolution of the fishing activity since the end of 4 s. ICSR October 25 landings (tons) 3 25 2 15 1 5 49-5 51-52 motorization 53-54 55-56 57-58 fishing season cold winter 59-6 61-62 63-64 65-66 67-68 69-7 18 16 14 12 1 8 6 4 2 Increase of landings in the beginning of 6 s did not allow to see over-fishing effects since motorization. fishing effort (.1 h) S iz e c o m p o s itio n p e r y e a r 2 4 6 8 1 12 s iz e ( c m )
Bay of Brest: evolution of the fishing system 195-1963 (method of geometrical locus). ICSR October 25 cpue (t+1) 25 2 15 1 5 (1972, 1973) 5 1 15 2 25 cpue (t) (195, 1951) motorization (1963, 1964) (1953, 1954) severe winter The motorization caused a first deep change of the equilibrium. Ten s later a second change underwent. No significant changes after even if the current dynamic of the stock is positive.
Bay of Brest: evolution of the fishing system until the middle of 5 s. ICSR October 25 abundance (1 6 scallops) 8 7 6 5 4 3 2 1 1949 195 1951 1952 1953 1954 1955 Gr6+ Gr5 Gr4 Gr3 Gr2 Gr1 3 2.5 2 1.5 1.5 1949 195 1951 1952 1953 1954 1955 Two main age-groups dominated the stock («fishery of recruitment»). Over-fishing (see ratio R/C). No scallop fishery has made out by so high catch rate of the age-group 1. The whole catch capacity was very close to the agegroup 2 one. Catch capacity of the age-group 2 is closely correlated with abundance (ρ=.967). F sel q q(gr2) R/C
ICSR October 25 The Bay of Saint-Brieuc (period after 1962). Weak fishing traditions (apart from lobster until 188 and cod Icelandic long-line fisheries until 3 s). Merchant marine traditions. Warty venus has been fished since 1953. Scallop dynamics: After cyclical appearances (1925-29, 1947-49), the stock densities have become significant since the beginning of 6 s. Opposite population dynamics to scallops of the Bay of Brest: the severe winter 1963 strengthened the Channel stocks (collapse of predators: octopus).
Saint-Brieuc Bay: evolution of the main fishing parameters for 4 s. ICSR October 25 landings (tons) fishing effort (hours) 14 12 1 8 6 4 2 6 5 4 3 2 1 1962 1972 1982 1992 22 1962 1972 1982 1992 22 yield per hour (kg) engine power (ch) 12 1 2 18 16 14 12 1 8 6 4 2 8 6 4 2 1962 1972 1982 1992 22 New vessels («golden period») New vessels (linked to subsidy policy) 196 1965 197 1975 198 1985 199 1995 2 25 The spectacular increase of catches between 1965 and 1975 not only due to recruitment: catch capacities grew up. Landings declined in 1975-199 (new built vessels). Management plan based only on reduction of fishing effort (divided by 7). Even with weak recruitments (middle of 9 s), LPUE are high. Mean engine power changed gradually and it is currently stable.
Saint-Brieuc Bay: management scheme since license system (1974). ICSR October 25 landings (ton) 12 1 8 6 4 2 72 mm 85 mm 92 mm 16m 294kW 1974 1976 1978 198 1982 1984 1986 1988 199 1992 1994 1996 1998 2 22 13m 185kW 3 25 2 15 1 5 recrutement (millions) landings recruitment Years 6-7: elementary management plans («fishery of recruitment»). The fishery became more independent of the abundance of only one agegroup (smoothed variations). However, early exploitation of some classes (e.g. born 1989, 199, 1995).
ICSR October 25 Standardized fishing mortality -> reliable description of the catch capacity capturabilité (tous groupes confondus) 2.5 2. 1.5 1..5. Lim = 1989 α =.25 b =.443 c = 2.138 SCE =.99 R² =.877 q i= b. cvi c 197 1975 198 1985 199 1995 2 25 année c.[1+ α.( i Lim)] q i= b. i cv Catchability vs. engine power (cv i ) before Lim (i < Lim) Catchability vs. engine power (cv i ) + technical progress (coeff. α) after Lim (i Lim) Increase of catch capacities up to 12-14% per. Strongth growth correlated with entry of new vessels (middle of 8 s). After 1989 no effect of engine power (stable): assimilation of technical progress allows increase of 2.5 %/.
ICSR October 25 Conclusion. - Recent history: effect of the global warming in spite of cyclical variations of temperatures revealing periodicity of 7-8 s. - Both analysed stocks present different features of demographic pattern (PAULET, 199) as well as for fishery development. - Bay of Brest: not regulated mecanization and undersized catches. Before 1963, the stock declined gradually for 1 s. - Bay of Saint-Brieuc: more strict regulations (selectivity of dredges, market size), but catch capacities have grown continually (+12-14% per ). - Traditional regulation policy seems to run out because of computing developments on board (+2.5% per ).