Batoid Abundances, Spatial Distribution, and Life History Traits in the Strait of Sicily (Central Mediterranean Sea): Bridging a Knowledge Gap through Three Decades of Survey

Abstract

Batoid species play a key role in marine ecosystems but unfortunately they have globally declined over the last decades. Given the paucity of information, abundance data and the main life history traits for batoids, obtained through about three decades of bottom trawl surveys, are presented and discussed. The surveys were carried out in two areas of the Central Mediterranean (South of Sicily and Malta Island), in a timeframe ranging from 1990 to 2018. Excluding some batoids, the abundance trends were stable or increasing. Only R. clavata, R. miraletus, and D. oxyrinchus showed occurrence and abundance indexes notable enough to carry out more detailed analysis. In particular, spatial distribution analysis of these species highlighted the presence of two main hotspots in Sicilian waters whereas they seem more widespread in Malta. The lengths at first maturity (L50) were 695 and 860, 635 and 574, and 364 and 349 mm total length (TL), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The asymptotic lengths (L∞) and the curvature coefficients (K) were 1365 and 1240 (K = 0.11 and 0.26), 1260 and 1100 (K = 0.16 and 0.26), and 840 and 800 mm TL (K = 0.36 and 0.41), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The lack of detailed quantitative historical information on batoids of Sicily and Malta does not allow to analytically judge the current status of the stocks, although the higher abundance of some species within Malta raises some concern for the Sicilian counterpart. In conclusion, suitable actions to protect batoids in the investigated area are recommended.

Influence of ecological traits on spatio-temporal dynamics of an elasmobranch community in a heavily exploited basin

“…These species showed either a continuous positive trend from the mid 1990s or an increase in the most recent years. Similarly to our results, recent increase in abundance for thornback skate and small-spotted catshark were also dected in the South of Sicily 33,34 and in the North Sea 35 , suggesting convergent patterns in historically heavily exploited areas that have experienced recent reduction in fishing effort. A negative trend since 1994 was previously detected for spurdog 7 and our results show that its abundance remained steady at a low level in the past two decades.…”

Strongly structured populations and reproductive habitat fragmentation increase the vulnerability of the Mediterranean starry rayRaja asterias(Elasmobranchii, Rajidae)

“…The Mediterranean starry ray is described as a minor commercial species at the regional and subregional levels (Food and Agriculture Organization of the United Nations, 2020) and appears among the skate species most affected by high rates of bycatch in multispecies trawl fisheries (Biton‐Porsmoguer & Lloret, 2020; Geraci et al, 2021). An essential step in the implementation of conservation policies of biological resources is the knowledge of the population unit boundaries.…”

Prvi nalaz mača srebrenjaka Trachipterus trachypterus Gmelin 1789 (Lampriformes) u Sicillijanskom tjesnacu

“…& G.W. POTTS 1990;GERACI et al, 2019;GERACI et al, 2021). The present study widens the spatial distribution of the species to the Mediterranean and sheds light on some biological aspects such as reproductive features and age estimation.…”