Chondrichthyes - Multidisciplinary Approach

Filho, Luis Fernando da Silva Rodrigues; Sales, João Bráullio de Luna

doi:10.5772/65879

Cited by 6 publications

(1 citation statement)

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“…Thus, it becomes crucial to better understand biology, ecology, population structure and dynamics of these fish stocks, and whether they are directly exploited or caught as bycatch. A glaring example are elasmobranchs (Class Chondrichthyes, subclass Elasmobranchii) which play an important role in the deep sea as top predators and are particularly vulnerable to impacts due to their life-history strategies such as low lifetime fecundities, slow growth rates, late age at maturity and high longevities (5). Even worse is the lack of information for the second class of cartilaginous fishes, the chimaeras (Class Chondrichthyes, subclass Holocephali) that are still regarded as one of the most mysterious groups in the deep sea for which very few data are available.…”

Section: Introductionmentioning

confidence: 99%

On the genetic diversity of Chimaera monstrosa Linnaeus, 1758 (Chordata, Chondrichthyes, Holocephali) in the Mediterranean Sea

Carugati,

Cappelletti,

Melis

et al. 2024

Front. Fish Sci.

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The sustainable management and conservation of deep-sea species may be hampered by the paucity of data on their population structure and connectivity, in the face of ever-increasing fisheries pressure and other forms of impacts on deep-sea ecosystems. The rabbit fish, Chimaera monstrosa, is a deep-sea cartilaginous fish, reported worldwide in the past, but currently distributed only in the North-Eastern Atlantic Ocean and Mediterranean Sea. It is currently experiencing high levels of mortality associated with by-catch. Its slow growth, low fecundity and late maturity make this species particularly vulnerable to anthropogenic impact, although little is known about processes of connectivity between ecoregions. This study utilized DNA sequencing of the mitochondrial cytochrome c oxidase subunit I (COI) gene to investigate the population structure and demography of C. monstrosa both at the small (around the coasts of Sardinia, western Mediterranean Sea) and at larger spatial scales (at the pan-Mediterranean level, and between the Atlantic Ocean and the Mediterranean Sea). A total of 100 new sequences were obtained from specimens of Mediterranean origin, identifying 15 new haplotypes out of the 30 known so far for the species. Evidence of feeble but significant differentiation was detected among locations within the Tyrrhenian basin. Bayesian clustering analyses indicated the occurrence of three distinct haplogroups: the most common spread all over the Mediterranean, and the other two limited to the Western basin. Greater levels of genetic differentiation were found between the Atlantic and Mediterranean populations which constituted two main genetic clusters, with no shared haplotypes. The two populations became separated at the end of the Middle Pleistocene, with a clear sign of demographic expansion during the same period. The rabbit fish constitutes an important exception to a general paradigm of deep-sea species being connected by high levels of gene flow and such results could be useful to implement current management strategies to conserve this vulnerable by-caught species.

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Section: Introductionmentioning

confidence: 99%

On the genetic diversity of Chimaera monstrosa Linnaeus, 1758 (Chordata, Chondrichthyes, Holocephali) in the Mediterranean Sea

Carugati,

Cappelletti,

Melis

et al. 2024

Front. Fish Sci.

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Against Common Assumptions, the World’s Shark Bite Rates Are Decreasing

Ritter

Amin

Cahn

2019

Journal of Marine Biology

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The trends of the world’s top ten countries relating to shark bite rates, defined as the ratio of the annual number of shark bites of a country and its resident human population, were analyzed for the period 2000-2016. A nonparametric permutation-based methodology was used to determine whether the slope of the regression line of a country remained constant over time or whether so-called joinpoints, a core feature of the statistical software Joinpoint, occurred, at which the slope changes and a better fit could be obtained by applying a straight-line model. More than 90% of all shark bite incidents occurred along the US, Australia, South Africa, and New Zealand coasts. Since three of these coasts showed a negative trend when transformed into bite rates, the overall global trend is decreasing. Potential reasons for this decrease in shark bite rates—besides an increase in the world’s human population, resulting in more beach going people, and a decrease of sharks due to overfishing—are discussed.

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Batoid Abundances, Spatial Distribution, and Life History Traits in the Strait of Sicily (Central Mediterranean Sea): Bridging a Knowledge Gap through Three Decades of Survey

Geraci

Ragonese

Scannella

et al. 2021

Animals

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Batoid species play a key role in marine ecosystems but unfortunately they have globally declined over the last decades. Given the paucity of information, abundance data and the main life history traits for batoids, obtained through about three decades of bottom trawl surveys, are presented and discussed. The surveys were carried out in two areas of the Central Mediterranean (South of Sicily and Malta Island), in a timeframe ranging from 1990 to 2018. Excluding some batoids, the abundance trends were stable or increasing. Only R. clavata, R. miraletus, and D. oxyrinchus showed occurrence and abundance indexes notable enough to carry out more detailed analysis. In particular, spatial distribution analysis of these species highlighted the presence of two main hotspots in Sicilian waters whereas they seem more widespread in Malta. The lengths at first maturity (L50) were 695 and 860, 635 and 574, and 364 and 349 mm total length (TL), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The asymptotic lengths (L∞) and the curvature coefficients (K) were 1365 and 1240 (K = 0.11 and 0.26), 1260 and 1100 (K = 0.16 and 0.26), and 840 and 800 mm TL (K = 0.36 and 0.41), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The lack of detailed quantitative historical information on batoids of Sicily and Malta does not allow to analytically judge the current status of the stocks, although the higher abundance of some species within Malta raises some concern for the Sicilian counterpart. In conclusion, suitable actions to protect batoids in the investigated area are recommended.

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Chondrichthyes - Multidisciplinary Approach

Cited by 6 publications

References 0 publications

On the genetic diversity of Chimaera monstrosa Linnaeus, 1758 (Chordata, Chondrichthyes, Holocephali) in the Mediterranean Sea

On the genetic diversity of Chimaera monstrosa Linnaeus, 1758 (Chordata, Chondrichthyes, Holocephali) in the Mediterranean Sea

Against Common Assumptions, the World’s Shark Bite Rates Are Decreasing

Batoid Abundances, Spatial Distribution, and Life History Traits in the Strait of Sicily (Central Mediterranean Sea): Bridging a Knowledge Gap through Three Decades of Survey

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