Variation in fish condition within and between populations: the effect on their productivity and management implications (Mediterranean and North Atlantic) Josep Lloret (a), Hans-Joachim Rätz (b) and Montserrat Demestre (a) (a) Institut de Ciències del Mar (CMIMA-CSIC), Barcelona, Catalonia, Spain (b) Institut für Seefischerei, Hamburg, Germany UNESCO WORKSHOP June Varna (Bulgaria) LARGE-SCALE DISTURBANCES (REGIME SHIFTS) AND RECOVERY IN AQUATIC ECOSYSTEMS: CHALLENGES FOR MANAGEMENT TOWARDS SUSTAINABILITY

1. Condition (fitness) is an important feature of fishes because it affects growth, reproduction and mortality 2. Two areas: Mediterranean and North Atlantic 3. Several commercial demersal species: cod, white seabream, hake, red mullet, etc 4. Several sampling methods: groundfish surveys, data from fishery vessels, spear fishing 5. Several condition indices: K, HSI, DSI, GSI, total lipids (muscle and liver) 6. Publications: H.J. Rätz and J. Lloret. ICES Journal of Marine Science (in press) J. Lloret, R. Galzin, L. Gil de Sola, A. Souplet and M. Demestre. Journal of Fish Biology 67:1 (July; in press) J. Lloret and S. Planes. Marine Ecology Progress Series 248: H.J. Rätz, J. Lloret. Fisheries Research 60: J. Lloret, Gil de Sola, L., Souplet, A. and Galzin, R. ICES J. mar. Sci. 59: FISH CONDITION

CAUSES OF VARIABILITY IN FISH CONDITION

Habitat productivity

MEDITERRANEAN a) Condition is generally better in the north (Gulf of Lions: higher productivity) than in the south (Catalan Sea: lower productivity) b) Condition generally decreases with depth (deep waters: lower productivity) Rhône river Ebre river

K of Lophius budegassa MEDITERRANEAN

DSI of Pagellus acarne MEDITERRANEAN

(230) (38) ln % lipid dry weight Gulf of LionsCatalan Sea Total lipids in the muscle of Pagellus acarne MEDITERRANEAN

Total lipids in the muscle of Mullus surmuletus MEDITERRANEAN

Interannual fluctuations of K of Lophius piscatorius MEDITERRANEAN

Bottom characteristics

MEDITERRANEAN

(84) (46) Muscle lipid Liver lipid Rocky unprotected Sandy unprotected Condition of juvenile Diplodus sargus is better in the rocky coast than in the sandy coast % dry weight MEDITERRANEAN

Habitat protection

MEDITERRANEAN

(19) (41) HSI Muscle lipid Rocky protected Banyuls Rocky unprotected Condition of post-spawners D. sargus is better in the rocky protected area of Banyuls than in the adjacent rocky unprotected area Index (HSI) or % dry weight MEDITERRANEAN

(43) (32) (42) Muscle lipidLiver lipid Rocky Protected Cap Creus Rocky unprotected …and the same in the rocky protected area of Cap de Creus % dry weight 1 4 MEDITERRANEAN

Water temperature

Northwest Greenland Labrador Grand Bank Golf v. St. Lawrence Georges Bank NORTH ATLANTIC Northeast Northeast Arctic Iceland West of Scotland North Sea Irish Sea

NORTH ATLANTIC

SPATIAL VARIABILIY IN TEMPERATURE AND CONDITION r 2 =0,67, p=0,0036. NORTH ATLANTIC Cod stocks living in temperate waters are better conditioned than those living in cold waters

R 2 =0.28 Mean K= 0.89 INTERANNUAL VARIABILIY IN TEMPERATURE AND CONDITION IN GREENLAND NORTH ATLANTIC Condition is better when water temperature is higher than average

Stock density

NORTH ATLANTIC The strong year class 1984 of cod off Greenland experienced a low condition during the following years

Sex and reproductive stage

HSI M. barbatus DSI M. barbatus Juveniles Adult males Adult females HSI P. erythrinus Sex differences in condition Females are better conditioned than males; and adults better than juveniles MEDITERRANEAN

Differences in condition between different reproductive stages of D. sargus (Gulf of Lions) Post-spawners are better conditioned than spawners MEDITERRANEAN

Size (age) of fish

HSI of cod during resting (Greenland, autumn 1998; males + females) The bigger are better conditioned NORTH ATLANTIC

GSI of Mullus barbatus during spawning (NW Mediterranean; spring 2000&2001; females) MEDITERRANEAN The bigger are better conditioned

GSI of Diplodus sargus during spawning (Gulf of Lions; spring 2001; males) MEDITERRANEAN The bigger are better conditioned

CONSEQUENCES OF THE VARIABILITY IN CONDITION: EFFECTS ON STOCK PRODUCTIVITY AND MANAGEMENT IMPLICATIONS

Stock productivity

Growth of cod ( weight at age 4) r 2 =0,79, p=0,0006. Well conditioned cod stocks are more productive because they grow faster NORTH ATLANTIC

r 2 =0,49, p=0,0234. Well conditioned cod stocks are more productive because they recruit more successful at decreased stock sizes Recruitment potential of cod ( Ricker’s a-coefficient from the SSB-R relationships) NORTH ATLANTIC

Growth of cod off Greenland is faster when condition is better; r 2 = 0.50 NORTH ATLANTIC

Management implications

1.Poor conditioned populations are more susceptible to overexploitation 2.Low condition values recorded in given years can precede negative events in stock productivity in the following years: condition can be monitored to detect regime shifts and forecast changes in the productivity of stocks 3.Additional management measures are needed when poor condition values are recorded (in given years or habitats) In this sense, the protection of habitats can help to preserve the condition and status of fish stocks. NORTH ATLANTICMEDITERRANEAN TAKE CARE WITH POOR CONDITIONED FISH!