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Evidence of trawling impact on Hoplostethus mediterraneus in the central–eastern Mediterranean Sea
Vitale, S.; Ragonese, S.; Cannizzaro, L.; Fiorentino, F.; Mazzola, S. (2014). Evidence of trawling impact on Hoplostethus mediterraneus in the central–eastern Mediterranean Sea. J. Mar. Biol. Ass. U.K. 94(3): 631-640. hdl.handle.net/10.1017/S0025315413001884
In: Journal of the Marine Biological Association of the United Kingdom. Cambridge University Press/Marine Biological Association of the United Kingdom: Cambridge. ISSN 0025-3154, more
Peer reviewed article  

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Keywords
    Hoplostethus mediterraneus mediterraneus Cuvier, 1829 [WoRMS]; MED, Mediterranean [Marine Regions]; Marine
Author keywords
    Silver roughy; Deep-water trawling; Length structure; Stock status; Longevity overfishing

Authors  Top 
  • Vitale, S.
  • Ragonese, S.
  • Cannizzaro, L.
  • Fiorentino, F.
  • Mazzola, S.

Abstract
    The silver roughy, Hoplostethus mediterraneus is a benthopelagic cosmopolitan fish regularly caught as by-catch of the deep-water crustacean trawl fishery (CTF) in the central–eastern Mediterranean. Monthly samples of silver roughy were sampled from the catches of four commercial trawlers in 2004. Each trawler operated in different fishing grounds (FGs), located off Northern Tunisia, South of Sicily, Malta Islands and in South Levant, for which different exploitation levels are reported. The overall length–frequency distribution (LFD) was constructed, and fishing impact indices (length as percentage of LFD, optimum and maximum length, percentage of mega-spawners and total mortality/von Bertalanffy curvature ratio) were calculated. In spite of an overall acceptable status (juveniles, matures and mega-spawners were present in the catch), sampling data revealed significant differences in LFD shape and status indices between FGs. Those FGs traditionally considered more exploited (Northern Tunisia and South of Sicily) showed a dominance of juveniles, a rarefaction of mega-spawners, a reduction in maximum and asymptotic length and a higher Z/K ratio. Considering the general homogeneity of Mediterranean deep-water habitats, the pelagic dispersal of eggs and the poor swimming capabilities of silver roughy, the present results indicated that deep-water trawling may induce a slow and subtle, although significant, erosion of the older, late maturing and slow growing component of the stocks in the Mediterranean (so-called longevity-overfishing).

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