Accueil | << 1 2 >> |
![]() |
Gilman, E., Chaloupka, M., Bach, P., Fennell, H., Hall, M., Musyl, M., et al. (2020). Effect of pelagic longline bait type on species selectivity: a global synthesis of evidence. Rev. Fish. Biol. Fish., 30(3), 535–551.
Résumé: Fisheries can profoundly affect bycatch species with 'slow' life history traits. Managing bait type offers one tool to control species selectivity. Different species and sizes of marine predators have different prey, and hence bait, preferences. This preference is a function of a bait's chemical, visual, acoustic and textural characteristics and size, and for seabirds the effect on hook sink rate is also important. We conducted a global meta-analysis of existing estimates of the relative risk of capture on different pelagic longline baits. We applied a Bayesian random effects meta-analytic regression modelling approach to estimate overall expected bait-specific catch rates. For blue shark and marine turtles, there were 34% (95% HDI: 4-59%) and 60% (95% HDI: 44-76%) significantly lower relative risks of capture on forage fish bait than squid bait, respectively. Overall estimates of bait-specific relative risk were not significantly different for seven other assessed taxa. The lack of a significant overall estimate of relative capture risk for pelagic shark species combined but significant effect for blue sharks suggests there is species-specific variability in bait-specific catch risk within this group. A qualitative literature review suggests that tunas and istiophorid billfishes may have higher catch rates on squid than fish bait, which conflicts with reducing marine turtle and blue shark catch rates. The findings from this synthesis of quantitative and qualitative evidence support identifying economically viable bycatch management measures with acceptable tradeoffs when multispecies conflicts are unavoidable, and highlight research priorities for global pelagic longline fisheries.
|
Larsen, B. K., Skov, P. V., McKenzie, D. J., & Jokumsen, A. (2012). The effects of stocking density and low level sustained exercise on the energetic efficiency of rainbow trout (Oncorhynchus mykiss) reared at 19 degrees C. Aquaculture, 324, 226–233.
Résumé: A 9 week growth trial was performed at two rearing densities; low (similar to 25 kg m(-3)) and high (similar to 100 kg m-3), in combination with either static water or a water current corresponding to 0.9 body lengths s(-1), to investigate the effects of density and exercise on the bioenergetics of rainbow trout reared at 19 degrees C, particularly routine metabolic rate (RMR), specific growth rate (SGR), and feed conversion ratio (FCR). The growth trial showed that high rearing density resulted in significantly lower SGR and increased FCR, with no significant alleviating effects of a water current, although slight improvement in both parameters were observed at low density. A significant linear relationship between SGR and FCR suggested that increased energy expenditure was the primary cause of reduced growth. Hourly measurements of instantaneous oxygen uptake, during a period of similar growth (200-350 g), revealed clear effects of the experimental conditions. Energetic budgets were calculated from feed intake and routine metabolic rate (RMR) and revealed that whilst feed intake was similar for all groups, a higher RMR in the high density groups resulted in a higher daily rate of energy utilization for routine activity, leading to slower growth. However, a lower RMR in fish subjected to a current resulted in a greater proportion of energy being retained, leading to significantly higher SGR for the selected period, at both low and high density. Furthermore, the presence of a water current was observed to induce schooling behaviour, which is known to reduce aggression and stress. It is thereby likely that the presence of a current had a positive effect on welfare in addition to its effect on energy metabolism. We conclude that the presence of a water current to some extent could alleviate the negative effects of high density at 19 degrees C, a relatively high temperature experienced in farming of rainbow trout during hot seasons. (C) 2011 Elsevier B.V. All rights reserved.
Mots-Clés: Energetic budget; Rainbow trout; Rearing density; Routine metabolic rate; Schooling behaviour; Sustained exercise; Welfare; cardiorespiratory performance; charr salvelinus-alpinus; feeding-behavior; fish welfare; food-intake; juvenile arctic charr; oxygen-consumption; physiology; respiratory; salmon salmo-salar; seasonal temperature
|
McKenzie, D. J., Hoglund, E., Dupont-Prinet, A., Larsen, B. K., Skov, P. V., Pedersen, P. B., et al. (2012). Effects of stocking density and sustained aerobic exercise on growth, energetics and welfare of rainbow trout. Aquaculture, 338, 216–222.
Résumé: Two stocking densities, “low” (L, between similar to 19 and similar to 25 kg m(-3)) and “high” (H, between similar to 75 and similar to 100 kg m(-3)) were compared for effects on specific growth rate (SGR), feed conversion, energetics and welfare of rainbow trout reared at 14 degrees C either in static water (S) or swimming in a gentle current of similar to 0.9 bodylengths s(-1) (C). Trout (initial mass similar to 110 g) were reared for 9 weeks in circular tanks (volume 0.6 m(3)), in triplicate of four conditions (LS, LC, HS, HC). Fish were fed ad-libitum daily: waste pellets were swirl-collected at the outflow to calculate feed intake. SGR was measured each three weeks for the last six weeks of the trial. The tanks functioned as intermittent-stopped flow respirometers, to permit metabolic rate to be measured as instantaneous oxygen uptake once per hour. Mean (+/-SD) SGR was significantly lower at H than L (1.51 +/- 0.03 vs 1.44 +/- 0.04% day(-1), respectively, n = 6) and lowest in HC. When compared over a similar interval of mass gain, H groups had approximately 25% higher metabolic rates than L, with the highest rates in the HC condition. As a result, fish in the H groups dissipated a greater amount of feed energy as metabolism and, across all groups, there was a direct negative relationship between the quantity of energy dissipated and their SCR. There was no evidence of a neuroendocrine stress response, plasma cortisol was around 1 ng ml(-1) in all conditions. An acute crowding stress increased plasma cortisol to above 120 ng ml(-1) in all groups, but C groups recovered to control levels within 8 h whereas S groups required 20 h. Respirometry on individuals revealed that H fish had approximately 14% higher metabolic rates than L fish, indicating that increased metabolic rate in rearing tanks was in part physiological. The H groups had approximately 15% lower critical swimming speeds than the L groups which, together with their raised metabolic rate, indicated a physiological impairment Thus, high density reduced SGR by raising energy dissipation, at least partially as a physiological response by the fish, although there was no evidence of an endocrine stress response. The only beneficial effect of C was in recovery from acute stress. (C) 2012 Elsevier B.V. All rights reserved.
Mots-Clés: Aerobic scope; charr salvelinus-alpinus; Cortisol; Critical swimming speed; current issues; feeding-behavior; fish welfare; juvenile arctic charr; oncorhynchus-mykiss; respiratory physiology; respirometry; salmon salmo-salar; Stress; stress-response; swimming performance; Welfare indicator
|
Pennino, M. G., Bachiller, E., Lloret-Lloret, E., Albo-Puigserver, M., Esteban, A., Jadaud, A., et al. (2020). Ingestion of microplastics and occurrence of parasite association in Mediterranean anchovy and sardine. Mar. Pollut. Bull., 158, 111399.
Résumé: We quantified the incidence of microplastics in the gut contents of the European sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) in the Northwestern Mediterranean Sea and tested which variables influence this abundance, including the prevalence of parasites (i.e., trematoda larvae and nematodes). We detected a 58% occurrence of microplastics ingestion in sardines and a 60% in anchovies. With respect to sardines, the individuals with lower body conditions were found to have the highest microplastics ingestion probabilities, whereas in anchovies such probabilities were observed in individuals with higher gonadosomatic indices and smaller size. The areas with the highest microplastics ingestion probabilities were the Gulf of Alicante for sardines and the Gulf of Lion – Ebro Delta for anchovies. Both species showed a positive relationship between parasites and microplastics ingestion. These results highlight that both parasitism and ingestion of microplastics are concerns for the health of marine stocks and human consumers.
|
Queiros, Q., Fromentin, J. - M., Gasset, E., Dutto, G., Huiban, C., Metral, L., et al. (2019). Food in the sea: size also matters for pelagic fish. Front. Mar. Sci., 6, Unsp-385.
Résumé: Small pelagic fish are key components of marine ecosystems and fisheries worldwide. Despite the absence of recruitment failure and overfishing, pelagic fisheries have been in crisis for a decade in the Western Mediterranean Sea because of a marked decline in sardine size and condition. This situation most probably results from bottom-up control and changes in the plankton community toward smaller plankton. To understand such an unusual phenomenon, we developed an original and innovative experimental approach investigating the mechanisms induced by a reduction in the quantity and size of sardine prey. While experimentations offer the unique opportunity to integrate behavior and ecophysiology in understanding key demographic processes, they remain rarely used in fisheries science, even more so on small pelagics due to the notorious difficulty to handle them. The results revealed that food size (without any modification of its energy content) is as important as food quantity for body condition, growth and reserve lipids: sardines that fed on small particles had to consume twice as much as those feeding on large particles to achieve the same condition and growth. Such a strong impact of food size (based on 100 vs. 1200 mu m pellets) was unexpected and may reflect a different energy cost or gain of two feeding behaviors, filter-feeding vs. particulate-feeding, which would have to be tested in further study. As increasing temperature favors planktonic chains of smaller size, climate change might actually accelerate and amplify such phenomenon and thus strongly affect fisheries.
|