Evidence of trawling impact on Hoplostethus mediterraneus in the central–eastern Mediterranean Sea
ABSTRACT The silver roughy, Hoplostethus mediterraneus is a benthopelagic cosmopolitan fish regularly caught as by-catch of the deepwater
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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ABSTRACT: The main objective of this study was fo know the age of silver roughy. A sample oj274 silver roughies Hoplostethus mediterraneus (Cuvier; /829) (pisces; Thachichthyidae) with a standard /ength (SL) ranging berween 36 and /76 mm was col1ected, Otoliths increments were interpreted by three difJèrl?nJ age readers. The maximum age was Il yeors in fema/es and 1Q years in ma/es. The differences (years) in age estimated by each age reader through statistica/ tests, showed no significant differences.Biologia marina mediterranea. 01/2004; 11:661-665.