Temporal dynamics of demersal chondrichthyan species in the central western Mediterranean

Frontiers in Marine Science

Antonello Mulas¹ 

[1] University of Cagliari;

关键词: Mediterranean Sea;    distribution;    population structure;    chondrichthyans;    abundance;   

DOI  :  10.3389/conf.FMARS.2015.03.00194

来源: DOAJ

【 摘 要 】

The rapid expansion of fisheries and globalized trade are emerging as the principal drivers of coastal and ocean threat. Considering the important role of Chondrichthyes as predators at the top of food chain in marine ecosystems, knowledge on their biology remains scarce in the Mediterranean. In this regard, our objective is to give information on their spatial distribution, abundance and population structure. Data were collected for 25 demersal species, including batoid species, sharks and holocephalans from 1994 to 2013 during scientific bottom trawl surveys (MEDITS project) carried out around the Sardinian seas. The total frequency of occurrence (f%), the Biomass Index (BI, kg/km2), and the Density Index (DI, N/km2) were estimated for the continental shelf (10-200 m), slope (200-800 m), and overall (10-800 m) depth strata. Size trends were also calculated for the most abundant species considering all depth strata. The correlation among MEDITS figures (f%, BI, DI, size structure) and years were assessed by species computing the Pearson linear coefficient. From f% and abundance indexes investigation, only the small spotted catshark Scyliorhinus canicula and the thornback ray Raja clavata were ubiquitous in all strata investigated, instead, all the other species showed a preferential distribution for the shelf or the slope. In general, the temporal trends of BI and DI were stable or positive for both macro-strata, except for the longnose spurdog Squalus blainville which seemed to show a statistically significant decreasing trend. All analyzed species displayed temporal stable trends in size structure analysis, apart from Raja brachyura and Dipturus oxyrinchus that showed a statistically significant increase. Despite the time series analysis revealed stable or positive trends, it appears clear the need of urgent management measures to protect the demersal chondrichthyan species extending the monitoring over time and implementing the data collected by scientific and commercial trawl surveys.

【 授权许可】

Unknown