Search results for "bycatch"
showing 10 items of 24 documents
Mortality of pike-perch (Stizostedion lucioperca), brown trout (Salmo trutta) and landlocked salmon (Salmo salar m. sebago) caught as by-catch in pel…
2000
Altogether 146 pike-perch, 49 brown trout and 19 landlocked salmon were caught in 23 exploratory trawl-hauls in lake Pyhaselka, Finland. Brown trout and salmon were caught only in surface trawling, whereas pike-perch were taken also in mid-water trawling. Most of the fish were smaller than the minimal legal size of 40 cm. To estimate their post-trawling mortality, 129 fish were kept in net cages for 1 week. Less than 15% of the pike-perch and brown trout caught by surface trawl died during 1 week caging, whereas every caged salmon died. Mid-water trawling was far more lethal to pike-perch than surface trawling. We conclude that pike-perch and brown trout can recover from surface trawling. S…
Incidental catch of marine turtles by Spanish bottom trawlers in the western Mediterranean
2014
A questionnaire-based survey of fishermen was conducted in the Valencia region (eastern Spain) to assess the levels of marine turtle bycatch. Interviews covered 41.3% of the bottom trawling fleet in the region and included 111 fishermen (one per boat). Results were combined with those from previous studies conducted in neighbouring regions using the same methodology to assess the global impact of bottom trawling on the western Mediterranean stock of the loggerhead turtle (Caretta caretta). Estimated turtle catch per unit effort (CPUE) is 0.09 turtles per vessel per month, according to the information reported by fishermen. As a consequence, the whole fleet of bottom trawlers operating off t…
MEDLEM database, a data collection on large Elasmobranchs in the Mediterranean and Black seas
2020
The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains more than 3,000 records (with more than 4,000 individuals) of large elasmobranch species from 21 different countries around the Mediterranean and Black seas, observed from 1666 to 2017. The principal species included in the archive are the devil ray (1,868 individuals), the basking shark (935 individuals), the blue shark (622 individuals), and the great white shark (342 individuals). In the last decades, other species such as the thresher shark (187 individuals), the shortfin mako (180 individuals), and the spiny butterfly ray (138) were reported with increasing frequency. This was possibly due to increased public a…
First report of the scavenging isopod Natatolana neglecta (Crustacea: Isopoda: Cirolanidae) feeding on a sea turtle
2019
A juvenile male loggerhead sea turtle (Caretta caretta) was found dead in April 2015, entangled in a trammel net on the Mediterranean coast of Spain. Post-mortem examination revealed the presence of ninety-five isopods dispersed in the coelomic cavity, and inside the oesophagus and skull. All individuals found scavenging on the sea turtle were identified as Natatolana neglecta (Hansen, 1890) (Isopoda: Cirolanidae). Genetic analysis of the isopod gut contents showed that they were feeding on turtle tissue, confirming that N. neglecta can also attack dead sea turtles. This study shows the value of cirolanids as potential indicators of the cause of death in stranded sea turtles.
Monitoring the habitat use of common Bottlenose Dolphins (Tursiops truncatus) using passive acoustics in a Mediterranean marine protected area
2014
The Mediterranean Tursiops truncatus subpopulation has been classified as Vulnerable on the IUCN Red List because of its decline. This species in coastal areas is exposed to a wide variety of threats: directed kills, bycatch, reduced prey availability caused by environmental degradation and overfishing, habitat degradation including disturbances from boat traffic and noise. Despite the increase in boat traffic in the Mediterranean Sea, the effect on T. truncatus’ habitat use has been studied in little detail and few data have been published. This study represents the first attempt to characterise spatial and temporal habitat use by T. truncatus and its relation to boat traffic in the Isole …
Diet composition and seasonal feeding patterns of a freshwater ringed seal (Pusa hispida saimensis)
2014
The Saimaa ringed seal (Pusa hispida saimensis) is one of the few freshwater seal populations worldwide. The major conservation issue of this critically endangered population is bycatch mortality. We used digestive tract content and stable isotopes (d 13 Ca ndd 15 N) to estimate the diet and seasonal feeding patterns for gaining better understanding of the seals feeding habits and potential conservation implications. The diet was similar across age groups. Altogether 15 fish species were identified and the most important were smelt (Osmerus eperlanus), ruff (Gymnocephalus cernuus), perch (Perca fluviatilis), vendace (Coregonus albula )a nd cyprinids. The high d 15 N values suggested that th…
New historical data for long-term swordfish ecological studies in the Mediterranean Sea
2021
Abstract. Management of marine fisheries and ecosystems is constrained by knowledge based on datasets with limited temporal coverage. Many populations and ecosystems were perturbed long before scientific investigations began. This situation is particularly acute for the largest and commercially most valuable species. We hypothesized that historical trap fishery records for bluefin tuna (Thunnus thynnus Linnaeus, 1758) could contain catch data and information for other, bycatch species, such as swordfish (Xiphias gladius Linnaeus, 1758). This species has a long history of exploitation and is presently overexploited, yet indicators of its status (biomass) used in fishery management only start…
By-catch of cetaceans and other species of conservation concern during pair trawl fishing operations in the Adriatic Sea (Italy)
2010
By-catch is one of the main sources of anthropogenic mortality in marine species of conservation concern worldwide. Between 2006 and 2008, the Consorzio Nazionale Interuniversitario per le Scienze del Mare (CoNISMa) coordinated a monitoring programme of cetacean by-catch in Italian pelagic trawlers, funded in compliance with European Regulation 812/2004. Sixteen independent observers monitored a total of 3141 hauls. The observation coverage ranged between 0.9 and 6.3% of the regional fishing effort. Almost all by-catch events were recorded in the northern Adriatic Sea. By-catch rates of bottlenose dolphins (Tursiops truncatus) and loggerhead turtles (Caretta caretta) were 0.0006 and 0.0255 …
Spatio-temporal composition of discard associated with the deep water rose shrimp fisheries (Parapenaeus longirostris, Lucas 1846) in the south-centr…
2017
Discarding in fisheries is the fraction of the total catch brought on board and returned to the sea dead or alive for legal or economic reasons. The reduction of discard is one of the main objectives of the European Common Fishery Policy. This study aimed to improve the current knowledge of the discard associated with the deep-water rose shrimp (DPS) fisheries in the south-central Mediterranean Sea. We analyzed data collected from January 2009 to December 2013. Multivariate data analysis and generalized additive models (GAMs) were used to assess the spatio-temporal composition of the discard (which represented 36% of the total catch) and factors influencing its distribution. Multiple analys…
New records of leatherback sea turtle, Dermochelys coriacea (Vandelli, 1761) (Testudines: Dermochelyidae) in the Strait of Sicily
2017
We report three new records of leatherback sea turtle, Dermochelys coriacea (Vandelli, 1761) recovered in February 2011 and in spring-summer 2016 in the Strait of Sicily. The individuals were handed over dead to the IZS of Palermo for necropsy. The first specimen measured 139 and 91 cm of CCL and CCW respectively and was found beached and alive but died a few hours later for septicemia. The second measured 110 cm of CCL and 83 cm of CCW and showed a deep wound on its head probably due to contact with a boat propeller. The third individual measured 134 cm of CCL and 96 cm of CCW and had plastic bags, a piece of fishing net and debris of various nature in the stomach. For the second individua…