Preliminary assessment of discards survival in a multi‐species Mediterranean bottom trawl fishery

• Published in: Journal of applied ichthyology Vol. 34; no. 4; pp. 842 - 849
• Main Authors: Tsagarakis, K., Nikolioudakis, N., Papandroulakis, N., Vassilopoulou, V., Machias, A.
• Format: Journal Article
• Language: English
• Published: Berlin John Wiley & Sons, Inc 01.08.2018
• Subjects: Autumn; Bottom trawling; Common Fisheries Policy; Conger conger; Density stratification; Diplodus annularis; discard survival; Discards; Elasmobranchii; European Union; Experimental fishing; fish discards; Fisheries; fisheries law; Fishery policy; Fishing; Greece; hake; High temperature; Invertebrates; Ionian Sea; Landing; landing obligation; Marine fishes; Mediterranean Sea; Merluccius merluccius; Metalimnion; post‐catch mortality; Seasonal thermocline; seasonal variation; Seasons; Serranus; Species; Spring; Spring (season); Stocks; Stratification; Survival; survival rate; Tanks; Thermocline; trawling; Water column; Water stratification; Water temperature; Wildlife conservation; MED; Mediterranean Sea; Greece
• ISSN: 0175-8659; 1439-0426
• DOI: 10.1111/jai.13691

Summary The EU Common Fisheries Policy (CFP) reform establishes a gradual landing obligation for stocks for which catch limits are set, and in the Mediterranean for species with Minimum Conservation Reference Size. However, the landing obligation will not apply for species with scientific evidence of high survival rates. Discards estimates usually assume that the whole discarded catch is dead or dies at sea. However, survival of individuals discarded at sea is substantial for several species. In the Mediterranean Sea, the information on this issue is very limited. The aim of this study is to perform a preliminary assessment of the short‐term survival of discards in the multi‐species bottom trawl fishery in the Eastern Ionian Sea, Greece. Experimental fishing was held in spring when no water column stratification was observed and in autumn when a seasonal thermocline was formed. The catch was sorted, the regularly discarded species/sizes were put in tanks and their survival was monitored in specific time intervals up to 72 hr. A seasonal effect was obvious with high mortality in autumn being attributed to high water temperatures. Survival was low or zero for most species, but was relatively high for certain species (e.g., annular seabream, Diplodus annularis (Linnaeus, 1758); European conger, Conger conger (Linnaeus, 1758); brown comber, Serranus hepatus (Linnaeus, 1758) among bony fishes) and broad taxonomic categories (elasmobranchs and most invertebrates) in spring or in both seasons. Poor survival was generally estimated for most species subject to the landing obligation (e.g., hake, Merluccius merluccius (Linnaeus, 1758)). The present study, even though preliminary, can be important for improving future works, for identifying species with high survival potential, and—to a lesser extent—for the implementation of the CFP.