U potrazi za plijenom: pojava psine lisice, Alopias vulpinus (Bonnaterre, 1788) u sjevernom Jadranu i njegove interakcije s ribarstvom

The common thresher shark, Alopias vulpinus, has shown a marked decline in abundance in the Mediterranean Sea. Through the analysis of long-term fishery time series (1966–2013), this study highlights that an important driver of the presence of A. vulpinus in the northern Adriatic Sea, one of the most exploited basins of the Mediterranean, is the abundance of its prey, the sardine Sardina pilchardus. From 1997-2013, an annual average of 14 thresher sharks was landed at Chioggia (Italy), the main fish market in the area, mainly from July to October. More than 75% of the landed thresher sharks were sexually immature, with some specimens weighing less than 10 kg, indicating that a high proportion of the catch was composed of small young and newborn individuals. These results support the occurrence of a nursery area in the northern Adriatic Sea, highlighting the need for proper management of A. vulpinus catch in this area.Zabilježen je značajan pad zastupljenosti psa lisice, Alopias vulpinus, u Sredozemnom moru. Analizom dugoročnog vremenskog niza podataka u ribarstvu (1966-2013), ovo istraživanje pokazuje da je važan pokretač prisutnosti A. vulpinus, u sjevernom Jadranu kao jednom od najiskorištenijih bazena na Sredozemlju, obilje njegova plijena srdele, Sardina pilchardus. U razdoblju 1997.-2013. godišnji prosjek ulova psine lisice je iznosio 14 primjeraka donesenih na glavnu ribarnicu u mjestu Chioggia (Italija) i to poglavito od srpnja do listopada. Više od 75% primjeraka ulovljenog psa lisice bili su spolno nezreli, od kojih su neki primjerci imali manje od 10 kg, što ukazuje da je visok udio ulova bio sastavljen od malih nedoraslih jedniki i mlađi. Ovi rezultati podupiru pojavu rastilišta u sjevernom Jadranu, ujedno naglašavajući potrebu pravilnog upravljanja ulovom A. vulpinus u ovom području

U potrazi za plijenom: pojava psine lisice, Alopias vulpinus (Bonnaterre, 1788) u sjevernom Jadranu i njegove interakcije s ribarstvom

The common thresher shark, Alopias vulpinus, has shown a marked decline in abundance in the Mediterranean Sea. Through the analysis of long-term fishery time series (1966–2013), this study highlights that an important driver of the presence of A. vulpinus in the northern Adriatic Sea, one of the most exploited basins of the Mediterranean, is the abundance of its prey, the sardine Sardina pilchardus. From 1997-2013, an annual average of 14 thresher sharks was landed at Chioggia (Italy), the main fish market in the area, mainly from July to October. More than 75% of the landed thresher sharks were sexually immature, with some specimens weighing less than 10 kg, indicating that a high proportion of the catch was composed of small young and newborn individuals. These results support the occurrence of a nursery area in the northern Adriatic Sea, highlighting the need for proper management of A. vulpinus catch in this area.Zabilježen je značajan pad zastupljenosti psa lisice, Alopias vulpinus, u Sredozemnom moru. Analizom dugoročnog vremenskog niza podataka u ribarstvu (1966-2013), ovo istraživanje pokazuje da je važan pokretač prisutnosti A. vulpinus, u sjevernom Jadranu kao jednom od najiskorištenijih bazena na Sredozemlju, obilje njegova plijena srdele, Sardina pilchardus. U razdoblju 1997.-2013. godišnji prosjek ulova psine lisice je iznosio 14 primjeraka donesenih na glavnu ribarnicu u mjestu Chioggia (Italija) i to poglavito od srpnja do listopada. Više od 75% primjeraka ulovljenog psa lisice bili su spolno nezreli, od kojih su neki primjerci imali manje od 10 kg, što ukazuje da je visok udio ulova bio sastavljen od malih nedoraslih jedniki i mlađi. Ovi rezultati podupiru pojavu rastilišta u sjevernom Jadranu, ujedno naglašavajući potrebu pravilnog upravljanja ulovom A. vulpinus u ovom području

In search of prey: the occurrence of Alopias vulpinus in the northern Adriatic Sea and its interactions with fishery.

The common thresher shark, Alopias vulpinus, has shown a marked decline in abundance in the Mediterranean Sea. Through the analysis of long-term fishery time series (1966\u20132013), this study highlights that an important driver of the presence of A. vulpinus in the northern Adriatic Sea, one of the most exploited basins of the Mediterranean, is the abundance of its prey, the sardine Sardina pilchardus. From 1997-2013, an annual average of 14 thresher sharks was landed at Chioggia (Italy), the main fish market in the area, mainly from July to October. More than 75% of the landed thresher sharks were sexually immature, with some specimens weighing less than 10 kg, indicating that a high proportion of the catch was composed of small young and newborn individuals. These results support the occurrence of a nursery area in the northern Adriatic Sea, highlighting the need for proper management of A. vulpinus catch in this area

Contrasting life history and reproductive traits in two populations of Scyliorhinus canicula

The role of natural and sexual selection in generating variability in biological traits between populations represents an intriguing issue in evolutionary biology. Considering their occurrence in different environments and the extensive incidence of post-copulatory sexual selection, elasmobranchs represent an interesting, yet still poorly investigated group. In this study, the life history and reproductive traits of two populations of Scyliorhinus canicula from the northern Adriatic Sea and the Strait of Sicily were compared. Differences in maximum size and size at sexual maturity were observed. The two populations also displayed differences in male and female genitalia. Males in the northern Adriatic Sea presented heavier testes, longer epididymis, seminal vesicles and claspers compared with those in the Strait of Sicily, suggesting the occurrence of stronger sperm competition at the former site. Similarly, females in the northern Adriatic Sea showed heavier oviducal glands and longer reproductive tracts compared with those in the Strait of Sicily. The coevolution between male and female genitalia suggests the occurrence of stronger sexual conflict and/or cryptic female choice in the population from the northern Adriatic Sea. Therefore, natural selection, represented by the different selective pressures occurring at different latitudes, and sexual selection, represented by potentially differing strengths of post-copulatory sexual selection and sexual conflict, may act individually in driving divergence in life history and reproductive traits in these two populations of S. canicula

<b>Trophic partitioning among three meso-predator shark species inhabiting the Northern Adriatic Sea</b>

While the general diet of Mediterranean elasmobranchs is well studied, little is known on food partitioning and competition among sympatric species, despite these being important forces structuring marine communities. Using stomach content and stable isotope analyses, we investigated diet and trophic level and evaluated diet overlap and partitioning of Scyliorhinus canicula, Mustelus mustelus, and M. punctulatus in the northern Adriatic Sea.</p

Resolving the ambiguities in the identification of two smooth-hound sharks (Mustelus mustelus and Mustelus punctulatus) using genetics and morphology

Elasmobranch species are among themost threatened marine fish, and sound biological data for many of them are lacking. In this context, the smooth-hounds (Mustelus spp., Triakidae, Carcharhiniformes) represent an intriguing genus, being characterized by unclear and sometimes contrasting diagnostic traits. Here, we present new insights into the identification of two closely related species, M. mustelus and M. punctulatus.The use of three different molecular markers on a dataset of 588 specimens highlighted a genetic distinction between the two species. However, whereas microsatellites provided unambiguous results in all the samples, the other two markers were not able to assign a fraction of the individuals (6.6% for cytochrome c oxidase subunit 1, 14.4% for Internal Transcribed Spacer 2), suggesting the occurrence of heteroplasmy and introgression due to past hybridisation events. The comparison between morphological traits, previously suggested as diagnostic for species identification, and genetic identification, enabled validation of the most reliable and practical morphological traits for species identification. The shape of the dermal denticles represents the most reliable trait, but its use during fieldwork may be impractical. The black spots on body sides were present almost exclusively in M. punctulatus, allowing its identification; however, their absence is not diagnostic for M. mustelus. The distance of the nostrils and the shape of the mouth are useful to distinguish the two species during fieldwork. Our results will allow an accurate identification of the two species leading to the collection of reliable data on their distribution, life history traits, exploitation and status of conservation

Ecological vulnerability of the chondrichthyan fauna of southern Australia to the stressors of climate change, fishing and other anthropogenic hazards

We develop a potentially widely applicable framework for analysing the vulnerability, resilience risk and exposure of chondrichthyan species to all types of anthropogenic stressors in the marine environment. The approach combines the three components of widely applied vulnerability analysis (exposure, sensitivity and adaptability) (ESA) with three components (exposure, susceptibility and productivity) (ESP) of our adaptation of productivity–susceptibility analysis (PSA). We apply our 12-step ESA‒ESP analysis to evaluate the vulnerability (risk of a marked reduction of the population) of each of 132 chondrichthyan species in the Exclusive Economic Zone of southern Australia. The vul nerability relates to a species’ resilience to a spatial (or suitability) reduction of its habitats from exposure to up to eight climate change stressors. Vulnerability also relates to anthro pogenic mortality added to natural mortality from exposure to the stressors of five types of fishing and seven other types of anthropogenic hazards. We use biological attributes as risk factors to evaluate risk related to resilience at the species or higher taxonomic level. We evaluate each species’ exposure to anthropogenic stressors by assigning it to one of six ecological groups based on its lifestyle (demersal versus pelagic) and habitat, defined by bathymetric range and substrates. We evaluate vulnerability for 11 scenarios: 2000– 2006 when fishing effort peaked; 2018 following a decade of fisheries management reforms; low, medium and high standard future carbon dioxide equivalent emissions sce narios; and their six possible climate–fishing combinations. Our results demonstrate the value of refugia from fishing and how climate change exacerbates the risks from fishing.Fil: Walker, Terence I.. Monash University; Australia. The University of Melbourne; AustraliaFil: Day, Robert W.. The University of Melbourne; AustraliaFil: Awruch, Cynthia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Tasmania; AustraliaFil: Bell, Justin D.. Institute For Marine And Antarctic Studies; AustraliaFil: Braccini, Juan Matias. Wa Fisheries And Marine Research Laboratories; AustraliaFil: Dapp, Derek R.. Monash University; AustraliaFil: Finotto, Licia. Monash University; AustraliaFil: Frick, Lorenz H.. Monash University; AustraliaFil: Garcés-García, Karla C.. Universidad Veracruzana; México. The University of Melbourne; AustraliaFil: Guida, Leonardo. Monash University; AustraliaFil: Huveneers, Charlie. Flinders University; AustraliaFil: Martins, Camila L.. Monash University; AustraliaFil: Rochowski, Bastien E.A.. The University of Melbourne; AustraliaFil: Tovar-Ávila, Javier. Inapesca; MéxicoFil: Trinnie, Fabian I.. Wa Fisheries And Marine Research Laboratories; AustraliaFil: Reina, Richard D.. Monash University; Australi

Contrasting life history and reproductive traits in two populations of Scyliorhinus canicula

The role of natural and sexual selection in generating variability in biological traits between populations represents an intriguing issue in evolutionary biology. Considering their occurrence in different environments and the extensive incidence of post-copulatory sexual selection, elasmobranchs represent an interesting, yet still poorly investigated group. In this study, the life history and reproductive traits of two populations of Scyliorhinus canicula from the northern Adriatic Sea and the Strait of Sicily were compared. Differences in maximum size and size at sexual maturity were observed. The two populations also displayed differences in male and female genitalia. Males in the northern Adriatic Sea presented heavier testes, longer epididymis, seminal vesicles and claspers compared with those in the Strait of Sicily, suggesting the occurrence of stronger sperm competition at the former site. Similarly, females in the northern Adriatic Sea showed heavier oviducal glands and longer reproductive tracts compared with those in the Strait of Sicily. The coevolution between male and female genitalia suggests the occurrence of stronger sexual conflict and/or cryptic female choice in the population from the northern Adriatic Sea. Therefore, natural selection, represented by the different selective pressures occurring at different latitudes, and sexual selection, represented by potentially differing strengths of post-copulatory sexual selection and sexual conflict, may act individually in driving divergence in life history and reproductive traits in these two populations of S. canicula