82 research outputs found
Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea
Coastal and demersal chondrichthyans, such as the small-spotted catshark, are expected to exhibit genetic differentiation in areas of complex geomorphology like the Mediterranean Basin because of their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial cytochrome c oxidase subunit I gene and 12 nuclear microsatellite loci in order to investigate the genetic structure and historical demography of this species, and to identify potential barriers to gene flow. Samples were collected from the Balearic Islands, the Algerian Basin, the Ionian Sea, the Corinthian Gulf and various locations across the Aegean Sea. Additional sequences from the Atlantic and the Levantine Basin retrieved from GenBank were included in the mitochondrial DNA analysis. Both mitochondrial and nuclear microsatellite DNA data revealed a strong genetic subdivision, mainly between the western and eastern Mediterranean, whereas the Levantine Basin shared haplotypes with both areas. The geographic isolation of the Mediterranean basins seems to enforce the population genetic differentiation of the species, with the deep sea acting as a strong barrier to its dispersal. Contrasting historical demographic patterns were also observed in different parts of the species' distribution, most notably a population growth trend in the western Mediterranean/
Atlantic area and a slight decreasing one in the Aegean Sea. The different effects of the Pleistocene glacial periods on the habitat availability may explain the contrasting demographic patterns observed. The current findings suggest that the smallspotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed
Evidence of high genetic connectivity for the longnose spurdog Squalus blainville in the Mediterranean Sea
Squalus blainville is one of the least studied Mediterranean shark species. Despite being intensively fished in several locations, biological knowledge is limited and no genetic structure information is available. This is the first study to examine the genetic structure of S. blainville in the Mediterranean Sea. Considering the high dispersal potential inferred for other squalid sharks, the hypothesis of panmixia was tested based on a 585 bp fragment of the mitochondrial DNA cytochrome c oxidase subunit I gene from 107 individuals and six nuclear microsatellite loci from 577 individuals. Samples were collected across the Ionian, Aegean and Libyan Seas and off the Balearic Islands. Twenty three additional sequences of Mediterranean and South African origin were retrieved from GenBank and included in the mitochondrial DNA analysis. The overall haplotype diversity was high, in contrast to the low nucleotide diversity. Low and non-significant pairwise ΊST and FST values along with a Bayesian cluster analysis suggested high connectivity with subsequent genetic homogeneity among the populations studied, and thus a high dispersal potential for S. blainville similar to other squalids. The historical demography of the species was also assessed, revealing a pattern of population expansion since the middle Pleistocene. These findings could be considered in species-specific conservation plans, although sampling over a larger spatial scale and more genetic markers are required to fully elucidate the genetic structure and dispersal potential of S. blainville
Histochemical analysis of glycoconjugates in the domestic cat testis
The localization and characterization of
oligosaccharide sequences in the cat testis was
investigated using 12 lectins in combination with the Ăelimination
reaction, N-Glycosidase F and sialidase
digestion. Leydig cells expressed O-linked glycans with
terminal aGalNAc (HPA reactivity) and N-glycans with
terminal/internal aMan (Con A affinity). The basement
membrane showed terminal Neu5Aca2,6Gal/GalNAc,
GalĂ1,3GalNAc, a/ĂGalNAc, and GlcNAc (SNA, PNA,
HPA, SBA, GSA II reactivity) in O-linked oligosaccharides,
terminal GalĂ1,4GlcNAc (RCA120 staining)
and aMan in N-linked oligosaccharides; in addition,
terminal Neu5Aca2,3GalĂ1,4GlcNac, Forssman
pentasaccharide, aGal, aL-Fuc and internal GlcNAc
(MAL II, DBA, GSA I-B4, UEA I, KOH-sialidase-WGA
affinity) formed both O- and N-linked oligosaccharides.
The Sertoli cells cytoplasm contained terminal Neu5Ac-
GalĂ1,4GlcNAc, Neu5Ac-ĂGalNAc as well as internal
GlcNAc in O-linked glycans, aMan in N-linked
glycoproteins and terminal Neu5Aca2,6Gal/
GalNAc in both O- and N-linked oligosaccharides.
Spermatogonia exhibited cytoplasmic N-linked
glycoproteins with aMan residues. The spermatocytes
cytoplasm expressed terminal Neu5Aca2,3GalĂ1,4
GlcNAc and GalĂ1,3GalNAc in O-linked oligosaccharides,
terminal GalĂ1,4GlcNAc and a/ĂGalNAc
in N-linked glycoconjugates. The Golgi region showed
terminal Neu5aca2,3GalĂ1,4GlcNac, GalĂ1,4GlcNAc,
Forssman pentasaccharide, and aGalNAc in O-linked
oligosaccharides, aMan and terminal ĂGal in N-linked
oligosaccharides. The acrosomes of Golgi-phase
spermatids expressed terminal GalĂ1,3GalNAc,
GalĂ1,4GlcNAc, Forssmann pentasaccharide,
a/ĂGalNAc, aGal and internal GlcNAc in O-linked
oligosaccharides, terminal a/ĂGalNAc, aGal and
terminal/internal aMan in N-linked glycoproteins. The
acrosomes of cap-phase spermatids lacked internal
Forssman pentasaccharide and aGal, while having
increased a/ĂGalNAc. The acrosomes of elongated
spermatids did not show terminal GalĂ1,3GalNAc,
displayed terminal GalĂ1,4GlcNAc and a/ĂGalNAc in
N-glycans and Neu5Ac-GalĂ1,3GalNAc in O-linked
oligosaccharides
Mitigating slipping-related mortality from purse seine fisheries for small pelagic fish: case studies from European Atlantic waters
The release of unwanted catches (UWC) from purse seines, while the catch is still in the water, is known as âslippingâ. Once thought to be a benign process, compared to discarding UWC overboard from the fishing vessel, it is now recognised that âslippingâ can lead to significant mortality in the released fish if done inappropriately. In this chapter, we examine purse seining and slipping operations, and discuss what drives slipping and potential mitigation measures to reduce slipping mortality. We use three examples of purse seine fisheries for small pelagic species in the North-east Atlantic; from Norway, Portugal and Spain. The ideal solution (identifying and avoiding UWC before the net is set) requires the development of tools to enable fishers to better characterise target schools in terms of key selection criteria, e.g., with respect to species, individual size and catch biomass. Such tools are being developed, based primarily on hydro-acoustic technology. However, some UWC in purse seine catches are inevitable, and operational improvements in slipping practices have been shown to significantly reduce stress and mortality in the released UWC. We conclude with a discussion on the challenges currently facing the implementation of the European Union (EU) Landing Obligation with regards to minimising slipping related mortality.info:eu-repo/semantics/publishedVersio
Report of the 2006 ICCAT workshop for bluefin tuna direct ageing
This report provides the presentations, discussions and conclusions from the ICCAT bluefin
tuna workshop for direct ageing held in Santander, Spain, in April 2006. The report
summarizes the ageing criteria used in the past and the agreements on future age determination
based on otoliths, vertebrae and spines. Advantages and disadvantages of each calcified
structure for ageing and border interpretation were discussed. It was considered that bluefin
tuna age interpretation becomes very difficult from age ten onwards using the whole vertebra
and the spine sections methods, but this last technique continues to be useful for older ages.
Otolith sections can be used for the whole age range. Participants agreed that none of these
three structures could be excluded from routine ageing because otoliths are not easily
available. Age estimations within the same structure and between different structures of the
same specimen were compared for several readers. Better precision was found between spine
readers compared to vertebra and otolith readers. Good age agreement was also achieved
between readers of spines and vertebrae from the same bluefin for ages less than 12 years.
Preliminary results from radiocarbon assays on otoliths were presented at the workshop and
gave promising outcomes for bluefin tuna age validation. Also, these suggested that bluefin
tuna can live longer than had previously been established and that a review is needed of the
currently used asymptotic size and growth rate for both stocks. Another important contribution
of the workshop was a manual for age interpretation.Le prĂ©sent rapport recueille les prĂ©sentations, discussions et conclusions de lâAtelier de
lâICCAT chargĂ© de la dĂ©termination directe de lâĂąge du thon rouge, tenu Ă Santander
(Espagne) au mois dâavril 2006. Le rapport rĂ©sume les critĂšres employĂ©s par le passĂ© pour
interprĂ©ter lâĂąge et les accords pour la dĂ©termination future de lâĂąge Ă partir des otolithes,
vertĂšbres et Ă©pines. LâAtelier a discutĂ© des avantages et des inconvĂ©nients de chaque structure
calcifiĂ©e pour dĂ©terminer lâĂąge et lâinterprĂ©tation du type de bord. On a abordĂ© la difficultĂ© de
lâinterprĂ©tation de lâĂąge des thons de plus de 10 ans au moyen de la vertĂšbre entiĂšre et des
sections des Ă©pines, bien que cette derniĂšre mĂ©thode continue dâĂȘtre utile pour les Ăąges
avancĂ©s. Les sections dâotolithes peuvent ĂȘtre employĂ©es pour toute la gamme dâĂąges. Les
participants ont convenu quâaucune de ces trois structures ne doit ĂȘtre exclue pour
lâinterprĂ©tation de lâĂąge parce quâil nâest pas toujours possible dâobtenir des otolithes. On a
comparĂ© les lectures de lâĂąge Ă lâintĂ©rieur de la mĂȘme structure et entre diffĂ©rentes structures
du mĂȘme exemplaire pour divers lecteurs. On a obtenu une plus grande prĂ©cision parmi les
lecteurs dâĂ©pines que parmi les lecteurs de vertĂšbres et dâotolithes. On a Ă©galement obtenu un
bon accord entre les lecteurs dâĂ©pines et de vertĂšbres originaires du mĂȘme exemplaire pour les
ùges inférieurs à 12 ans. Les résultats préliminaires des essais de radiocarbone dans les
otolithes ont Ă©tĂ© prĂ©sentĂ©s Ă lâAtelier, offrant de bonnes perspectives pour son utilisation dans la validation de lâĂąge. Ces rĂ©sultats indiquent aussi que le thon rouge a une plus grande
longĂ©vitĂ© que ce qui avait Ă©tĂ© auparavant Ă©tabli et quâil est nĂ©cessaire de rĂ©viser la longueur
asymptotique et le taux de croissance actuellement utilisĂ©s. LâĂ©laboration dâun manuel aux fins
de lâinterprĂ©tation de lâĂąge a constituĂ© une autre contribution importante de lâAtelier.Este informe recoge las presentaciones, discusiones y conclusiones del congreso de ICCAT
para la determinaciĂłn directa de la edad de atĂșn rojo, celebrado en Santander, España, en
abril de 2006. El informe resume los criterios empleados en el pasado para interpretar la edad
y los acuerdos para la determinación futura de la edad a partir de otolitos, vértebras y espinas.
Se discutieron las ventajas y los inconvenientes de cada estructura calcificada para determinar
la edad y la interpretaciĂłn del tipo borde. Se planteĂł la dificultad en la interpretaciĂłn de la
edad de atunes mayores de 10 años utilizando la vértebra entera y las secciones de espinas, no
obstante este Ășltimo mĂ©todo continĂșa siendo Ăștil para edades mayores. Las secciones de
otolitos pueden ser empleadas para todo el rango de edades. Los participantes acordaron que
ninguna de estas tres estructuras deben excluirse para la interpretaciĂłn de la edad porque no
siempre es posible obtener los otolitos. Se compararon las lecturas de edad dentro de la misma
estructura y entre diferentes estructuras del mismo ejemplar para varios lectores. Se obtuvo
una mayor precisiĂłn entre lectores de espinas comparada con las obtenidas por los lectores de
vértebras y otolitos. También se obtuvo un buen acuerdo entre lectores de espinas y vértebras
procedentes del mismo ejemplar para edades menores de 12 años. Los resultados preliminares
de las pruebas de radiocarbono en otolitos fueron presentados en el congreso, proporcionando
buenas expectativas para su uso en la validación de la edad. Estos resultados también indican
que el atĂșn rojo es mĂĄs longevo de lo que se consideraba y que es necesaria una revisiĂłn de la
longitud asintĂłtica y de la tasa de crecimiento empleadas actualmente. Otra importante
contribuciĂłn del congreso fue la elaboraciĂłn de un manual para la interpretaciĂłn de la edad
Fin Spine Bone Resorption in Atlantic Bluefin Tuna, Thunnus thynnus, and Comparison between Wild and Captive-Reared Specimens
Bone resorption in the first spine of the first dorsal fin of Atlantic bluefin tuna (ABFT) has long been considered for age estimation studies. In the present paper spine bone resorpion was assessed in wild (aged 1 to 13 years) and captive-reared (aged 2 to 11 years) ABFT sampled from the Mediterranean Sea. Total surface (TS), solid surface (SS) and reabsorbed surface (RS) were measured in spine transverse sections in order to obtain proportions of SS and RS. The spine section surface was found to be isometrically correlated to the fish fork length by a power equation. The fraction of solid spine bone progressively decreased according to a logarithmic equation correlating SS/TS to both fish size and age. The values ranged from 57% in the smallest examined individuals to 37% in the largest specimens. This phenomenon was further enhanced in captive-reared ABFT where SS/TS was 22% in the largest measured specimen. The difference between the fraction of SS of wild and captive-reared ABFT was highly significant. In each year class from 1- to 7-year-old wild specimens, the fraction of spine reabsorbed surface was significantly higher in specimens collected from March to May than in those sampled during the rest of the year. In 4-year-old fish the normal SS increase during the summer did not occur, possibly coinciding with their first sexual maturity. According to the correlations between SS/TS and age, the rate of spine bone resorption was significantly higher, even almost double, in captive-reared specimens. This could be attributed to the wider context of systemic dysfunctions occurring in reared ABFT, and may be related to a number of factors, including nutritional deficiencies, alteration of endocrine profile, cortisol-induced stress, and loss of spine functions during locomotion in rearing conditions.VersiĂłn del editor4,411
MEDLEM database, a data collection on large elasmobranchs in the Mediterranean and Black Seas
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 awareness on the conservation status of sharks, and the consequent development of new monitoring programs. MEDLEM does not have homogeneous reporting coverage throughout the Mediterranean and Black seas and it should be considered as a database of observed species presence. Scientific monitoring efforts in the south-eastern Mediterranean and Black seas are generally lower than in the northern sectors and the absence of some species in our database does not imply their actual absence in these regions. However, the available data allowed us to analyse the frequency and spatial distribution of records, the size frequencies for a few selected the available data allowed us to analyse the frequency and spatial distribution of records, the size frequencies for a few selected species, the overall area coverage, and which species are involved as bycatch by different fishing gears
Spatial and Sex-Specific Variation in Growth of Albacore Tuna (Thunnus alalunga) across the South Pacific Ocean
Spatial variation in growth is a common feature of demersal fish populations which often exist as discrete adult sub-populations linked by a pelagic larval stage. However, it remains unclear whether variation in growth occurs at similar spatial scales for populations of highly migratory pelagic species, such as tuna. We examined spatial variation in growth of albacore Thunnus alalunga across 90° of longitude in the South Pacific Ocean from the east coast of Australia to the Pitcairn Islands. Using length-at-age data from a validated ageing method we found evidence for significant variation in length-at-age and growth parameters (Lâ and k) between sexes and across longitudes. Growth trajectories were similar between sexes up until four years of age, after which the length-at-age for males was, on average, greater than that for females. Males reached an average maximum size more than 8 cm larger than females. Length-at-age and growth parameters were consistently greater at more easterly longitudes than at westerly longitudes for both females and males. Our results provide strong evidence that finer spatial structure exists within the South Pacific albacore stock and raises the question of whether the scale of their âhighly migratoryâ nature should be re-assessed. Future stock assessment models for South Pacific albacore should consider sex-specific growth curves and spatial variation in growth within the stock
Comparison of otolith growth and morphology with somatic growth and age in young-of-the-year bluefin tuna
Otolith morphological characteristics were studied using image analysis techniques and the relationships between otolith growth and somatic growth and age, as estimated from counting daily otolith increments, were examined in young-of-the-year (YOY) bluefin tuna Thunnus thynnus ranging in fork length (LF) from 8·5 to 55·5 cm. Whole otolith length, width, area and perimeter, and three shape indexes, circularity, E value and rectangularity, were extracted for each pair of sagittae. Since no statistical significant differences between left and right otolith morphometrics were found, only one otolith from each fish was used for correlations. Statistically significant relationships were observed between otoliths measurements and fish somatic growth when a linear regression was applied after logarithmic transformation of all variables tested. Among the variables, otolith length was the one that showed the highest correlation with LF, followed by otolith area and perimeter, whereas otolith rectangularity exhibited the lowest correlation. Statistically significant relationships were also observed between the otolith variables tested and the age of the fish, which ranged from 20 to 129 days. The ages estimated using otolith mass were very close to those assessed using daily increment counts (bias ranged from 1 to 24 days). Therefore, otolith mass could represent a valuable criterion for age estimation in YOY bluefin tuna that is objective, economic and easy to perform compared to daily increment counting method. © 2006 The Fisheries Society of the British Isles
- âŠ