1,721,019 research outputs found
New record of the great white shark Carcharodon carcharias from Lampedusa
Full text linkThis new record confirms that the Central Mediter ranean, and Sicilian coasts in particular, still represent a key area for the population of Mediterranean white
sharks, but also for other shark species (Bilecenoglu et al., 2013); in fact, 43% of all white shark sightings in the Italian seas (Micarelli et al., 2011) are from this area
Notes on a rare case of bluntnose sixgill shark hexanchus griseus stranded on the coast of tuscany in the central tyrrhenian sea [Note su un raro caso di spiaggiamento di capopiatto hexanchus griseus lungo la costa toscana nel mar tirreno centrale]
No full textA rare stranding event involving a 297 cm long mature male bluntnose sixgill shark (Hexanchus griseus) occurred on the Tuscan coast in the central Tyrrhenian Sea. The stranded specimen had 6 rows of teeth indicating that it
belonged to the H. griseus and not to the Hexanchus nakamurai species, which only has 5. Biometric data on two teeth of the left front region of the lower jaw were collected. The body of the specimen did not show evidence of
capture, only a deep cut at the height of the orbital arch suggesting a crash or the ramming of a boat
Influence of Male Presence on the Socıal Structure of Lesser Spotted Dogfısh (Scyliorhinus canicula) Female Groups
Full text linkSexual segregation in the lesser spotted dogfish (Scyliorhinus canicula) is most likely driven by the female strategy of avoidance of the males, which causes the formation of female groups in the nooks and shelters on the seafloor. This strategy allows them to reduce the multiple events of male sexual advances, which are energetically expensive. In order to examine the existence of a social structure in female lesser spotted dogfish aggregations and the impact of the presence of males on them, we analyzed the structure of the social network and the temporal stability of the associations of two populations each one including five females. An easy insertion of the males in female population was made possible by the presence of a homogeneous initial social structure with quite weak bonds. The social structure is regulated by differences in the individual behaviour, resulting in different strength and stability of aggregations of conspecifics.
The addition of the males produced a reduction of the Average Association Index and of the measures related to the populations’ network, strength of the associations and level of indirect connections of the individual. The presence of the males seems to have a greater effect on the individuals that are more weakly linked; while key individuals typically reduce their network values, but remain well integrated in the population; peripheral individuals have more variables values. This result indicates that relations exist between the sex, which is in contrast with the hypothesis of the female avoidance of males, which should produce strong and stable female groups. The actual knowledge of the behaviour and distribution of the Mediterranean lesser spotted dogfish does not prove the existence of a sexual segregation in this species. Based on the results we can assume that the home-ranges of females and males are not separated and that the male presence does not trigger a female aggregation mechanism. It is noteworthy that males have a destructive effect on the female associations, as these ones have shown a reduction of all the values. This might suggest that, in nature, the male presence and therefore the potential male sexual coercion may cause the spatial dispersion of the individuals of the population and reduce the cohesion of the group
Preliminary Observations on the Ability to Adapt To Salinity Changes in Nursehound Scyliorhinus Stellaris (Linnaeus, 1758) and Small Spotted Catsharks Scyliorhinus Canicula
Full text linkNursehound Scyliorhinus stellaris and small spotted catsharks Scyliorhinus canicula are frequently hosted in public
aquaria and their husbandry is improving. The reproduction of this species in captive conditions is not difficult and
juveniles are easily maintained in laboratory or in thematic tanks showed to the public. Data on juveniles are easily
acquired in order to understand different aspects of their natural life and physiology. In two stages, during 2006 and
2010, six S. stellaris and three S. canicula juveniles were tested at different salinity levels under controlled conditions in
order to understand their responses in terms of respiration rate to this stress. In fact this is a benthic species living at
constant water quality parameters at approximately 70-100 meters deep
Evidence of Sperm Storage in Nursehound (Scyliorhinus stellaris, Linnaeus 1758): Juveniles Husbandry and Tagging Program
Full text linkNursehound, Scyliorhinus stellaris (Linnaeus 1758), is a shark of the Scyliorhinidae family, close to the Scyliorhinus canicula (Linnaeus 1758), frequently hosted in public aquaria. Information on biology and ecology is deficiently available regarding this species of sharks. In the Mediterranean basin, they are occasional rare and vulnerable species (Serena, 2005). In 2003 a female specimen of Scyliorhinus stellaris, 90 cm long, fished in the Tyrrhenian Sea was transferred to Tuscany Argentario Mediterranean Aquarium and placed in a 20.000 L tank. The female laid 42 eggs and juveniles were born on 2004 and 2005. They were transferred to the aquarium laboratory in order to get standard protocol for correct juveniles husbandry. After a total of 18-month observations, some of them were tagged and let free on 2006. To collect data about nursehound shark needs in terms of feeding and growing in captivity, especially during the first life years, is a necessary and fundamental step in order to develop a Mediterranean program of tagging and study in the field of conservation policy proposal. Husbandry protocol for this species’ juveniles was developed in this study. This is the first reported case of a nursehound storing sperm for 2 years, in captivity (Pratt, 1993; Hamlett et al., 2002; Awruch, 2007)
Husbandry of tropical benthonic sharks (Chiloscyllium griseum, C. punctatum and Atelomycterus marmoratus): First step to develop protocols for controlled breeding with conservation purpose
No full textIn the IUCN Red List Chiloscyllium griseum, C. punctatum and Atelomycterus marmoratus are considered as "Near Threatened" species. Presently, there is a lack of information about their general biology, especially concerning reproduction and population structure. No monitoring measures are carried out by the fishing industry in order to enforce a suitable management plan for sustainable fisheries; additionally, Aquarium demand for these species is actually growing. The development of protocols and programmes in order to breed sharks can be very important for conservation purposes. In the Aquarium Mondo Marino, the Shark Study Centre (Centro Studi Squali), is actually working with the aim to get several couples of parents of the three above mentioned species in order to formalise the protocols for correct husbandry for breeding. The programme plans several steps: A) acclimatise young sharks, controlling feeding and Size rate, B) test different reproduction techniques C) improve eggs development and D) to stabilise juvenile Size. Keywords: shark breeding, Chiloscyllium griseum, Chiloscyllium punctatum, Atelomycterus marmoratu
First toxicological study in two commercial shark species from a Mediterranean Marine Protected Area
No full textLarge urban and industrial settlements, and the intense maritime traffic make the Mediterranean one of the most polluted areas in the world. This basin hosts considerable marine biodiversity, including many elasmobranchs, which are extremely vulnerable to environmental contamination due their life history traits. The impact of this threat on the cartilaginous fishes is still poorly studied, as well as the possible consequences for human health, in case of consumption of sharks, are uncertain. To fill this knowledge gap, quantitative and qualitative assessments of three groups of persistent organic pollutants (POPs) were carried out in the muscle and liver of two shark species, Mustelus punctulatus and Mustelus mustelus, caught in the Marine Protected Area (MPA) of Egadi Islands (South-Central Mediterranean Sea) between 2021 and 2023. As sharks are one of the top predators inhabiting the MPA, they can be considered a bioindicator of the local environmental status. Paradoxically, although M. punctulatus and M. mustelus have considerable commercial value for human consumption in the MPA, they are listed as Vulnerable by the IUCN in the Mediterranean. Regarding POPs levels, the results showed a trend of PCBs > DDTs >> HCB in liver and muscle for both species. Our results can significantly contribute to clarify the toxicological status of these species, allowing a first evaluation of the real risks both for the local marine life and for human health
Behavioural responses of white sharks to specific baits during cage diving ecotourism
Full text linkThis study describes the effect of different baits on the attraction, surface behaviour and conditioning of white sharks Carcharodon carcharias during local ecotourism activities. The sightings, behaviours, and pictures used for photographic identification were obtained during August to November 2012-2014 onboard tourist boats in Guadalupe Island, Mexico. Four types of baits were used: (1) frozen bait; (2) frozen bait and natural chum; (3) fresh fish bait; and (4) mackerel bags. Data were analysed according to sex, maturity and the total of sharks using 6,145 sightings of 121 white sharks. The type of bait showed no significant difference on the effectiveness to attracting sharks. Ethological analysis showed that the type of bait had a significant effect on the shark's surface behaviour during its interactions with boats. Natural chum and fresh baits showed short term behavioural patterns constituted by increased number of violent interactions with the bait, while the frozen bait did not generate a defined behavioural pattern. Conditioning of white sharks was determined by the number of interactions and the consumption frequency of the bait. Fifty nine percent of sharks (n=41) showed no conditioning, 36% (n=25) showed a low risk and only 5% (n=3) were found to have a high risk of conditioning. The results suggest that current ecotourism has no effect on the conditioning of the white sharks, and that all baits have a similar effectiveness for attracting the sharks. However, a different behavioural pattern was observed when fresh bait and chum were used, which could increase the potential of accidents during ecotourism
Preliminary observations about white shark's (Carcharodon carcharias) discriminatory patterns during surface predatory activity and type of approach
Full text linkThe aim of the present study was to gather information on the behaviour of great white shark Carcharodon carcharias during surface predatory activities. According to the present results, vision plays an important role in feeding patterns and appears correlated to weather conditions
DORSAL FIN PHOTOIDENTIFICATION: TOOL FOR LONG TERM STUDIES OF WHITE SHARK (CARCHARODON CARCHARIAS) BEHAVIOUR
Full text linkStudying the behaviour of the White Shark is a recent and big challenge. Optimising the
photoidentification of White Shark dorsal fins is a basic goal, in order to compare ehavioural information in both immature and mature specimens and between females and males. During a 6 years research, from 2009 to 2014, we observed about 296 sharks and 8 specimens were resighted several times. Data about sex, sizes, environmental
conditions and behaviours were collected. This is the first step to develop a more complex database in which include all the observed behaviors for each shark in different environmental conditions over the years. The final goal is to share the information we have collected with other research groups operating in other geographic areas working on other populations of white shark
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