Evidence of a spawning area for the bluefin tuna (Thunnus thynnus L.) in the eastern Mediterranean

Karakulak, F. Saadet; Oray, I. K.; Corriero, Aldo; Deflorio, M.; Santamaría, N.; Desantis, Salvatore; Metrio, G. De

doi:10.1111/j.1439-0426.2004.00561.x

Cited by 75 publications

(60 citation statements)

References 6 publications

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“…Such a difference in ageat-maturity between eastern and western populations is difficult to support in terms of reproductive physiology and ecology, hence further investigations on bluefin tuna reproduction in the West Atlantic and Mediterranean are needed with a view to clarifying these and other discrepancies. The classical list of Mediterranean spawning sites (Balearic archipelago and southern Thyrrhenian Sea) has recently been extended, with the addition of 2 spawning grounds located in the Levantin Sea (Karakulak et al 2004, Oray & Karakulak 2005 and around Malta (A. Corriero pers. comm.).…”

Section: Introductionmentioning

confidence: 99%

Influence of sampling gear in assessment of reproductive parameters for bluefin tuna in the western Mediterranean

Medina¹,

Abascal²,

Aragón³

et al. 2007

Mar. Ecol. Prog. Ser.

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Comparative histological and stereological analysis of gonads from longline-and purse seine-caught Atlantic bluefin tuna Thunnus thynnus was undertaken to assess the reproductive potential of the population in the western Mediterranean breeding area. Bluefin tuna sampled by purse seine clearly had higher gonadosomatic index values (GSI) than those caught by longline. While no remarkable histological differences were found between purse seine-and longline-caught males, the ovarian histology indicated a higher level of maturity in females from purse-seine samples, where most specimens were found to be in active spawning (AS). Within the longline sample the proportion of active spawning females was considerably higher at the end of the fishing season (midJune to mid-July) than earlier in May to mid-June (52.8 vs. 24%). Stereological analyses revealed that the samples collected by the 2 sampling gears differed primarily in the numbers of migratorynucleus oocytes, which were overwhelmingly more abundant in purse-seine catches, with average relative fecundity: 59 oocytes g -1 vs. 1.2 oocytes g -1 (purse-seine vs. longline). The frequency of ovaries with postovulatory follicles (POFs) in purse seine-caught bluefin tuna was 83.7%, equivalent to a spawning interval of 1.2 d; in contrast, only 32.6% of the females in longline catches had POFs, representing a spawning interval of 3.1 d. Assuming an average individual duration of the spawning process of 14 d, and considering the estimates of fecundity and spawning interval obtained from purse-seine samples, the average annual fecundity of bluefin tuna in the Balearic spawning ground would be approximately 77 × 10 6 eggs (relative fecundity of 702 eggs g -1 BW [body weight]).

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Section: Introductionmentioning

confidence: 99%

Influence of sampling gear in assessment of reproductive parameters for bluefin tuna in the western Mediterranean

Medina¹,

Abascal²,

Aragón³

et al. 2007

Mar. Ecol. Prog. Ser.

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“…Size-dependent movements and spawning in different areas and periods have been documented (15,(21)(22)(23). Genetic variation among three geographical samples suggested that at least two subpopulations inhabit and persist over short time periods (3 years) in the western and eastern Mediterranean Sea, yielding Wright's genetic variance (F ST ) values within the Mediterranean Sea between 0.0007 and 0.0087 (12,24).…”

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confidence: 99%

Spatio-temporal population structuring and genetic diversity retention in depleted Atlantic Bluefin tuna of the Mediterranean Sea

Riccioni

Landi²,

Ferrara³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

115

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Fishery genetics have greatly changed our understanding of population dynamics and structuring in marine fish. In this study, we show that the Atlantic Bluefin tuna (ABFT, Thunnus thynnus), an oceanic predatory species exhibiting highly migratory behavior, large population size, and high potential for dispersal during early life stages, displays significant genetic differences over space and time, both at the fine and large scales of variation. We compared microsatellite variation of contemporary (n = 256) and historical (n = 99) biological samples of ABFTs of the central-western Mediterranean Sea, the latter dating back to the early 20th century. Measures of genetic differentiation and a general heterozygote deficit suggest that differences exist among population samples, both now and 96-80 years ago. Thus, ABFTs do not represent a single panmictic population in the Mediterranean Sea. Statistics designed to infer changes in population size, both from current and past genetic variation, suggest that some Mediterranean ABFT populations, although still not severely reduced in their genetic potential, might have suffered from demographic declines. The short-term estimates of effective population size are straddled on the minimum threshold (effective population size = 500) indicated to maintain genetic diversity and evolutionary potential across several generations in natural populations.ancient DNA | effective population size | genetic structure | large pelagic fishes | Thunnus thynnus

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“…This period coincides with the species' spawning period in the region (Corriero et al 2003, Karakulak et al 2004, Heinisch et al 2008). More recently, Druon et al (2011) identified the potential bluefin tuna spawning season as occurring from mid-May to July, gradually building up from eastern to western Mediterranean waters.…”

Section: Discussionmentioning

confidence: 99%

Discovering where bluefin tuna, <i>Thunnus thynnus</i>, might go: using environmental and fishery data to map potential tuna habitat in the eastern Mediterranean Sea

Damalas¹,

Megalofonou²

2011

Sci. Mar.

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SUMMARY: Based on a dataset derived from commercial fisheries in the eastern Mediterranean Sea in 1998-2005, we applied generalized additive models (GAMs) to investigate the relative influence of a range of environmental factors on catch rates of Atlantic bluefin tuna (Thunnus thynnus Linnaeus, 1785). GAM analyses were conducted by separately modelling (1) the probability of making a catch (encountering a school), and (2) the positive catch rates (school size). Results suggested intra-annual variations in tuna distribution and revealed interesting associations with some environmental features, lunar periodicity being the most distinctive one. Probability of encountering a school peaked in late spring months, eastwards, at water temperatures above 22°C and around the full moon. Size of school was more likely to be larger in northeasternmost regions and in the vicinity of land in late spring, when the percentage of lunar disc illumination was higher. A moderate but continuous annual decline in the probability of encountering a bluefin tuna school was detected from the models' outputs. The models were used as an indication of preference or association for the selected environmental variables. Based on these associations, an indirect identification of the bluefin tuna potential habitat was obtained and used to map distributions in the eastern Mediterranean region.Keywords: bluefin tuna, GAM, habitat, SST, lunar index, Mediterranean, management. RESUMEN: Descubriendo a donde van los atunes rojos, Thunnus Thynnus: uso de datos ambientales y pesqueros en mapas del hábitat del atún en el Mediterráneo Oriental. -Se aplican modelos aditivos generalizados (GAMs) a la investigación de la influencia relativa de una serie de factores medioambientales en las tasas de captura de atún rojo Atlántico, mediante el uso de datos derivados de las capturas comerciales en el Mediterráneo oriental. Estos análisis se llevaron a cabo separadamente para: (1) la probabilidad de captura (encuentro con un banco) y (2) la tasa de captura (tamaño del banco). Ambos factores parecen variar a lo largo del año, y parecen estar asociados con algunos parámetros medioambientales, especialmente la fase lunar. La probabilidad de encontrar un banco de atún es mayor al final de la primavera, cuanto más al este, cuando la temperatura del agua supera los 22°C, y con luna llena. El tamaño del banco es probablemente mayor al final de la primavera, en la región noreste, cuando la luz del disco lunar es más intensa, y cerca de la costa. Los resultados muestran una disminución, moderada pero continua, de la probabilidad de encuentro con un banco de atún rojo. Ciertos modelos GAM se usaron como indicadores de la preferencia o asociación con ciertos factores ambientales. De acuerdo con estas asociaciones, se presenta una identificación indirecta del hábitat potencial del atún rojo, mostrando su distribución espacial en el Mediterraneo oriental.Palabras clave: atún rojo, GAM, hábitat, TSM, indice lunar, Mediterráneo, manejo. December 2012, 691-704, Barcelona (Spain...

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Evidence of a spawning area for the bluefin tuna (Thunnus thynnus L.) in the eastern Mediterranean

Abstract: no abstrac

Cited by 75 publications

References 6 publications

Influence of sampling gear in assessment of reproductive parameters for bluefin tuna in the western Mediterranean

Influence of sampling gear in assessment of reproductive parameters for bluefin tuna in the western Mediterranean

Spatio-temporal population structuring and genetic diversity retention in depleted Atlantic Bluefin tuna of the Mediterranean Sea

Discovering where bluefin tuna, <i>Thunnus thynnus</i>, might go: using environmental and fishery data to map potential tuna habitat in the eastern Mediterranean Sea

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