Influence of size, age and maternal condition on the oocyte dry weight of Argentine hake (Merluccius hubbsi)     

Gustavo J. Macchi  Marcelo Pjaro  María I. Militelli  Natalia Radovani  Lorena Rivas 《Fisheries Research》2006,80(2-3):345-349

Effects of maternal age–size and condition on oocyte dry weight were analysed for Merluccius hubbsi. Samples of mature females were collected in the Patagonian spawning area during 10 research surveys carried out between 2000 and 2005. Dry weight of 50 hydrated oocytes ranged from 0.80 to 1.90 mg. Relationships of this variable with total length and age were best described by a logarithmic model during the spawning peak. At the beginning and at the end of the reproductive season no significant relationship between these variables was observed, but a decrease in egg dry weight was detected during the spawning period. In general, young spawners (≤5-year-old) showed more variability in egg dry weight, which was associated with a reproductive season shorter than that of old females. Relative condition factor did not shows a significant relationship with oocyte dry weight, and mean values of this index were similar for different months of the spawning seasons analysed.  相似文献   

Dietary Lipid Requirements for Optimal Egg Quality of Redclaw Crayfish,Cherax quadricarinatus     

Hervey Rodríguez‐González  Humberto Villarreal  Manuel García‐Ulloa  Alfredo Hernández‐Llamas 《Journal of the World Aquaculture Society》2009,40(4):531-539

The effect of three crude dietary lipid levels (4, 8, and 12%) on egg quality of the female redclaw crayfish, Cherax quadricarinatus, was evaluated. Three replicate groups of 40 crayfish (mean initial weight ± SD, 23.0 ± 3.0 g) per diet treatment were stocked in 15,000 ‐L tanks, at 28 C. After 75 d of culture, there were significant differences (P < 0.001) in egg area (3.52–3.90 mm²), volume (34.0–39.3 mm³), weight (4.81–5.36 mg), and diameter (2.15–2.27 mm) in response to dietary lipids in the diet. Using the quadratic equation, the maximum responses of these parameters corresponded to lipid levels from 8.60–8.84%. There were no significant differences (P > 0.05) in survival (82.1–86.9%), final weight (41.0–43.7 g), number of spawning females (18.12–27.38%), and fecundity (9.07–10.31 eggs/g female). Additionally, there were no significant differences (P > 0.05) in egg mean protein (2306.87 ± 440.08 μg/egg), lipid (441.95 ± 83.23 μg/egg) and carbohydrate (74.81 ± 10.12 μg/egg) contents, and energy (13.49 ± 2.25 kcal/egg). The optimum overall response was obtained for dietary lipid content of 8.7%, which we recommend to optimize egg quality of this freshwater crayfish.  相似文献   

Do fish isotopic niches change in an Amazon floodplain lake over the hydrological regime?     

Lucas Silva Azevedo  Incio Abreu Pestana  Marcelo Gomes Almeida  Wanderley Rodrigues Bastos  Cristina Maria Magalhes Souza 《Ecology of Freshwater Fish》2022,31(1):72-80

Floodplain lakes are ecosystems characterised by annual flood and dry cycles. Fish ecology is influenced by the flood pulse due to the large influx of allochthonous food resources and diversification of habitats during the flood cycle, while during the dry cycle, fishes tend to be confined in reduced habitat. The aim of this study was to evaluate the seasonal variation in trophic niche width and overlap of four species—Mylossoma duriventre, Prochilodus nigricans, Cichla.pleiozona and Serrasalmus rhombeus—in an Amazonian floodplain lake. Stable isotope analyses were used to estimate trophic niche width and overlap during the flood and dry seasons. We hypothesised broader niche width for all species during the flood cycle and a higher degree of overlap between the two piscivorous fishes during the dry cycle. Isotopic niche width was 72% broader for P. nigricans, 61% for S. rhombeus and 54% for C. pleiozona during the dry cycle, which did not support our hypothesis. Core niche width overlaps were not observed between piscivorous species in either flood or dry cycle. The results indicate that seasonal variation in isotopic niche width is specific to feeding habit. Understanding how fish trophic ecology responds to changes in the hydrological regime during the seasons is crucial for sustainable fishery management in a region where many people rely heavily on fish for nutritional and economic purposes.  相似文献