Mortality and exploitation of marbled spinefoot, Siganus rivulatus (Actinopterygii: Perciformes: Siganidae), from southern Aegean Sea small-scale fishery

Abstract

Background. In the small-scale fisheries of the Gulf of Gökova (Turkish coast of the southern Aegean Sea) the marbled spinefoot, Siganus rivulatus Forsskål et Niebuhr, 1775, is a commercially important species. No sustainability study, however, has been carried out on the stock assessment and management of this species in the gulf. The aim of the presently reported study was to determine the mortality and biological reference points of Siganus rivulatus and suggest a proper fishery management plan for fishery regulations. Materials and methods. The sudy was conducted between July 2016 and June 2018. Fish samples were collected from the Gulf of Gökova small-scale fishery. The total mortality (Z), natural mortality (M), fishing mortality (F curr), and exploitation rate (E curr) were determined and compared with the biological reference points: the optimum fishing mortality (F opt), fishing mortality limit reference point (F lim), optimum exploitation rate (E opt). Results. Total mortality (Z), natural mortality (M), fishing mortality (F curr), and exploitation rate (E curr) were found to be 0.67, 0.32, 0.35, and 0.52, respectively. Furthermore, biological reference points (F opt , F lim , E opt) attained values of 0.16, 0.21, and 0.33 cm, respectively. Conclusion. The fishing pressure for Siganus rivulatus stocks the Gulf of Gökova should decrease for the sake of the sustainability of this resource.

Small-scale fishery catch composition in Rhodes (Eastern Mediterranean Sea)

“…Remarkably, the south Aegean areas where siganids are abundant, are also invaded by a wide variety of alien macrophytes (Tsiamis, 2012;ELNAIS, 2020); this complicates the issue and could lead to changes in the original-native structure of the bio-communities. As already mentioned, siganids are commercially important in the area under study, as in other invaded regions of the eastern Mediterranean (Turkey, Cyprus, Lebanon, Egypt, Libya, Israel) (Cerim et al, 2020;Soykan et al, 2020), contrarily to Crete where both siganids appeared later than in Rhodes, at the beginning of the year 2000, and, although common now (Skarvelis et al, 2015), they are still discarded (Authors, pers. comm.).…”

Maximization of fitness by phenological and phenotypic plasticity in range expanding rabbitfishes (Siganidae)

“…For instance, in Western Australia rabbitfish are not commonly targeted and only are caught as bycatch, yet the patterns between tropical and range‐extending populations held. Fisheries effect on the traits of S. rivulatus may be low in the Red Sea, because individuals were larger (>250 mm) despite that trammel nets used in the region select for fishes >150 mm (Saber & Gewida, 2020); however, we cannot discard a potential fishery effect in the Mediterranean Sea since nets target fishes >200 mm, which could include the oldest and bigger individuals (Cerim et al, 2020; Soykan, 2020). Nonetheless, the global analyses of maximum sizes were robust.…”

Persistence of tropical herbivores in temperate reefs constrains kelp resilience to cryptic habitats

“…K. biggibus and S. fuscescens in temperate reefs of Nagazaki, Japan, have been caught with gill nets, with parallel efforts to increase its acceptance and value in local fish markets (Kuwahara, 2015). Rabbitfish in the Mediterranean have become a common and well‐valued resource in several eastern countries (Cerim et al., 2020; EastMed, 2010). Similarly, in western Australia a small commercial fishery has been catching S. fuscescens, with diminishing landings along the years since 2012, indicating that continuous fishing could be effective to control their abundances (Lenanton et al., 2017).…”