Fish Species In Areas Research Articles

Spatial variation in the feeding strategies of Mediterranean fish: flatfish and mullet in the Gulf of Gaeta (Italy)

Marine coastal areas are highly productive due to the presence of various inputs of organic matter, including terrestrial material, which fuels food webs. However, the ecological mechanisms underlying the productivity of benthic and demersal fish species in estuarine areas are poorly understood. By means of C and N stable isotope analysis and Bayesian mixing models, we investigated the trophic niches of three common fish species: Citharus linguatula, Pegusa lascaris (flatfish) and Liza ramada (mullet) in the Gulf of Gaeta (Italy). Fish were collected from the north-western area and the south-eastern area of the Gulf of Gaeta, the latter affected by organic inputs from the Garigliano River. The results highlighted the riverine terrestrial origin of the organic matter at the base of the food web in the south-eastern area and marine autochthonous input in the north-western area. All fish species increased their trophic specialisation in proximity to the river mouth. L. ramada specialised on seston of terrestrial origin, reducing its niche overlap with C. linguatula and P. lascaris. Away from the river mouth, all species were characterised by longer individuals, increased intraspecific diet variability and higher interspecific similarity in resource use. Organic input from the river represented a complementary trophic niche axis that enabled lower interspecific niche overlap in the south-eastern area, where fish populations were found at higher densities. In conclusion, this study provided information about the effects of the flow of material from the basal compartment up to abundant fish species in areas enriched by organic matter of varying origin.

Assessing the Viability of Reintroduction of Locally Extinct Migratory Fish Brycon orbignyanus: Successful Growth, Dispersal and Maturation

The reintroduction of threatened fish species in areas where wild populations have been depleted due to anthropogenic impacts is an increasingly popular conservation tool and mitigation policy. Despite the importance of fish reintroduction for conservation purposes, little is known about its efficiency. Here, we assessed the viability of reintroduction of the endangered migratory fish, Brycon orbignyanus, in an area of the Upper Uruguay River basin where the species has not been reported for more than 30 years. We released 4000 yearling juveniles in the Pelotas River in 2014 and maintained 400 juveniles in captivity as a control population. After three years, a total of 13 individuals was recaptured, of which, 10 were considered sexually mature with first maturation being recorded in animals larger than 42 cm in total body length. The age–length comparison with a control population growth curve showed that recaptured fish were slightly bigger than those in captivity. Furthermore, important ecological attributes as schooling behavior and dispersal capacity were recorded for all recaptured individuals. Combined, our results suggest that the re-establishment of a self-sustained population of locally extinct species B. orbignyanus in the Pelotas River may be successful if sustained over time and supported by conservation policies.

Can bycatch in a flatfish gillnet fishery be reduced with rectangular mesh?

Gillnets fished in North Carolina, USA, estuaries have high rates of bycatch relative to the target catch of southern flounder, Paralichthys lethostigma Jordan & Gilbert. This study tested whether rectangular-mesh gillnets would maintain catch rates of southern flounder and reduce fish bycatch relative to conventional diamond-mesh gillnets in two North Carolina estuaries. In the Neuse River estuary, catch rates of legal southern flounder were not different between the two mesh shapes, but the bycatch of red drum, Sciaenops ocellatus (Linnaeus) and other fish species was reduced with rectangular-mesh net. In the Newport River estuary, southern flounder and red drum catches were reduced in rectangular-mesh net, but the decrease was greater for red drum. Catches of sublegal southern flounder were reduced in the rectangular-mesh net in both estuaries. Reduced catch rates of sublegal southern flounder and bycatch species suggest rectangular mesh may help manage stocks of estuarine fish species in areas where gillnets are used to target flatfishes.