Evidence of trawling impact on Hoplostethus mediterraneus in the Central-Eastern Mediterranean Sea

ArticleinJournal of the Marine Biological Association of the UK · January 2014with45 Reads
DOI: 10.1017/S0025315413001884
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).
  • [Show abstract] [Hide abstract] 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.
    Full-text · Article · Jan 2004 · Marine Biology
  • [Show abstract] [Hide abstract] ABSTRACT: Three simple fisheries indicators are presented: (i) percentage of mature fish in catch, with 100% as target; (ii) percent of specimens with optimum length in catch, with 100% as target; and (iii) percentage of ‘mega-spawners‘ in catch, with 0% as target, and 30–40% as representative of reasonable stock structure if no upper size limit exists. Application of these indicators to stocks of Gadus morhua, Sardinella aurita and Epinephelus aeneus demonstrate their usefulness. It is argued that such simple indicators have the potential to allow more stakeholders such as fishers, fish dealers, supermarket managers, consumers and politicians to participate in fisheries management and eventually hold and reverse the global pattern of convenience overfishing, which is defined here as deliberate overfishing sanctioned by official bodies who find it more convenient to risk eventual collapse of fish stocks than to risk social and political conflicts.
    Article · Mar 2004
  • [Show abstract] [Hide abstract] ABSTRACT: Data on the diet, feeding habits and daily rations of Hoplostethus mediterraneus Cuvier, 1829 in the bathyal eastern Ionian Sea (Mediterranean Sea) are presented. A total of 430 specimens collected by bottom trawls at depths ranging from 473 to 603m during four 24-h day–night sampling cycles covering the four annual seasons was examined. H. mediterraneus diet consisted of pelagic and vagile epibenthic prey, mainly crustaceans, and was dominated by benthopelagic natantian decapods (83.35% IRI, index of relative importance). Seasonal changes in diet were apparent and related to seasonal fluctuations in suprabenthic and zooplanktonic prey in the environment. Diel patterns in stomach fullness and trends in diel feeding cycles are discussed in relation to the vertical migratory movements of available prey (i.e. suprabenthos and zooplankton). Daily-ration estimates were determined by evacuation-rate models and ranged from 0.143% to 0.397% WW/WW. Overall, daily-ration estimates were within the range of the daily consumption of other deep-sea fish. Deduced from diet contents, we found a constant gross energy intake (305–316kcal g–1) during all seasons. As a possible response to the reproductive peak of mature females observed in summer, H. mediterraneus increases its food consumption, which, in turn, is coupled with an increase in food availability.
    Article · Apr 2005
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