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Ba, A., Schmidt, J., Deme, M., Lancker, K., Chaboud, C., Cury, P., et al. (2017). Profitability and economic drivers of small pelagic fisheries in West Africa: A twenty year perspective. Mar. Pol., 76, 152–158.
Résumé: Small pelagics are the main fish resource in North West Africa. In Senegal, these are mainly sardinellas (Sardinella aurita and S. maderensis) and bonga shad (Ethmalosa fimbriata). The fisheries, mainly encircling gillnets and purse seines, are predominantly performed by artisanal fishers and are of great importance for the Senegalese economy and for food security in the region. However, in recent years, the main conditions for these fisheries have changed and recent observations have shown strong declines in profit. An analysis over the last twenty years (1993-2013) show that the fisheries lost profit between 65% and 100% while operating costs increased by 25% and 90%, for encircling gillnet and purse seine, respectively. While the fuel price dominates as determining factor during the survey period, important other drivers during the last five years were a decrease in fish biomass and an increase in fishing effort.
Mots-Clés: Income; management; Senegal; small pelagic fish; Small scale fisheries
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Grande, M., Murua, H., Zudaire, I., Arsenault-Pernet, E. J., Pernet, F., & Bodin, N. (2016). Energy allocation strategy of skipjack tuna Katsuwonus pelamis during their reproductive cycle. J. Fish Biol., 89(5), 2434–2448.
Résumé: The lipid composition of somatic and reproductive tissues was determined for female skipjack tuna Katsuwonus pelamis caught in the western Indian Ocean between latitude 10 degrees N and 20 degrees S and longitude 40 degrees and 70 degrees E. The highest total lipid (TL) contents were in the liver and gonads, with white muscle levels approximately three-fold lower. Three lipid classes dominated: triacylglycerols (TAG), sterol esters and wax esters (SE-WE) and phospholipids (PL). Collectively, these accounted for between 70 and 80% of TLs. Changes in lipid concentrations were evaluated over the maturation cycle. Immature fish had the lowest gonad and liver TL levels; concentrations of TL, TAG, SE-WE and PL accumulated from immature to mature (spawning-capable) phase, reflecting sustained vitellogenic activity of the liver and a transfer of lipids to developing oocytes from the onset of vitellogenesis. Gonado-somatic and hepato-somatic indices were positively correlated with each other and positively related to TL in the gonads and liver. Fulton's condition index and lipid concentrations in muscle did not vary significantly over the maturation cycle; fat content in the main storage tissues was undepleted as the ovary developed. Hence, K. pelamis apparently supports reproduction directly from food intake over the breeding season. In the gonads, reserve lipids (SE-WE and TAG) and sterols were related to batch fecundity but this was not the case for somatic and hepatic tissues. These results suggest that K. pelamis utilizes an income breeding strategy.
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SALTON, M., SARAUX, C., DANN, P., & CHIARADIA, A. (2015). Carry-over body mass effect from winter to breeding in a resident seabird, the little penguin. Royal Society Open Science, 2(1), 140390.
Résumé: Using body mass and breeding data of individual penguins collected continuously over 7 years (2002–2008), we examined carry-over effects of winter body mass on timing of laying and breeding success in a resident seabird, the little penguin (Eudyptula minor). The austral winter month of July consistently had the lowest rate of colony attendance, which confirmed our expectation that penguins work hard to find resources at this time between breeding seasons. Contrary to our expectation, body mass in winter (July) was equal or higher than in the period before (‘moult-recovery’) and after (‘pre-breeding’) in 5 of 7 years for males and in all 7 years for females. We provided evidence of a carry-over effect of body mass from winter to breeding; females and males with higher body mass in winter were more likely to breed early and males with higher body mass in winter were likely to breed successfully. Sex differences might relate to sex-specific breeding tasks, where females may use their winter reserves to invest in egg-laying, whereas males use their winter reserves to sustain the longer fasts ashore during courtship. Our findings suggest that resident seabirds like little penguins can also benefit from a carry-over effect of winter body mass on subsequent breeding.
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Zudaire, I., Murua, H., Grande, M., Pernet, F., & Bodin, N. (2014). Accumulation and mobilization of lipids in relation to reproduction of yellowfin tuna (Thunnus albacares) in the Western Indian Ocean. Fisheries Research, , 50–59.
Résumé: Total lipid content and lipid class composition were analyzed in gonads, liver and white muscle of yellowfin tuna (Thunnus albacares) throughout ovary development to understand its reproductive allocation strategy and to assess the relation between female condition and reproduction. A total of 112 females were collected onboard purse-seiner in the Western Indian Ocean from January to March 2009, from June to July 2009, and from April to May 2010. Gonads were characterized by highly variable total lipid contents ranging from 5 to 27 μg mg−1 of wet weight (ww) with a predominance of neutral lipids, mainly triacylglycerols (TAG) and sterol- and wax-esters. The different lipid classes in gonads described an accumulative pattern through the maturity process from immature to hydration phase. Total lipid content in liver varied from 10 to 21 μg mg−1 ww, and serves as fuel for yellowfin tuna reproduction. TAG and phospholipid deposits became depleted as the ovary developed, suggesting a transfer of lipids directly from liver to the oocytes during vitellogenesis. In contrast, muscle total lipid content was low and constant throughout ovarian development (2.5–6 μg mg−1 ww). Hence, yellowfin tuna can be defined as an income-capital breeder species for which the cost of reproduction depends mainly on concurrent energy income from feeding and only little on stored lipids. Besides, no significant relationship between gonad lipid composition and fecundity was found in females able to spawn. Finally, the influence of yellowfin tuna aggregation behaviour on reproductive female condition has been investigated: gonad total lipid contents were higher in females caught in free-swimming schools than in females caught under fish aggregating devices (FADs). However, these results did not clarify whether the influence of FADs on associated yellowfin tuna affects their reproductive capacity.
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