جستجوی مقالات مرتبط با کلیدواژه « Longevity » در نشریات گروه « شیلات »

Glossogobius aureus is an important commercial fish for food supply and has been caught increasingly, but data on its population biology is limited. The present study was carried out along coastlines from Soc Trang to Bac Lieu, southern Vietnam to contribute new information on the biological characteristics of G. aureus population. Data analysis of length-frequency distribution of 666 individuals showed that the equation of von Bertalanffy curve of this species was . The species displayed 4.47 y longevity and 2.75 in the growth performance. The length-converted catch curve analysis showed that the fishing, natural and total mortalities were 2.73 yr-1, 1.52 yr-1 and 4.25 yr-1 respectively and fish exploitation rate was 0.64. There was one recruitment peak in July and the analyses of relative yield-per-recruit and biomass-per-recruit gave Emax=0.408, E0.1=0.284 and E0.5=0.404. This goby is potentially an aquaculture species due to its high growth rate. The fish stock has been overfished, so the gill net mesh size should be increased and fish should not be caught during the recruitment period for sustainable management.

This study is the first to compare age estimates based on scales and otoliths of the Nile tilapia, Oreochromis niloticus, from Lake Nasser, Egypt. Ageing precision between readers was estimated by calculating the percent agreement between three independent readers, and the coefficient of variation (CV) ages estimated from otoliths and scales. The relation between the total length of fish and the radius of its scale and otolith was determined and appeared to be linear. The estimated age composition of the O. niloticus included six age groups estimated using scales and five age groups estimated by otoliths. The relative precision (CV and SD) of ages estimated from otolith was higher than that from scales. Higher percentages of agreement of overall annuli identification and age assignment between readers were noted in otoliths comparing to that in scales. Scale showed some inaccurate estimation in the age of fish older than 4. The precision and bias information in this study will be beneficial to fisheries professionals in assessing the age of Nile tilapia and other cichlids in the future.

The effects of salinity, temperature, and light conditions on production and development, longevity, survival and sex ratios of the cyclopoid copepod, A. dengizicus were determined. Seven different salinity levels (5, 10, 15, 20, 25, 30, 35 psu), four temperatures (20, 25, 30, 35 °C), three different light intensities (33.3, 85.3, 162.1 μmol photons/ m2/ s) and light regimes (24:0, 0:24, and 12:12 h light:dark regime) were employed. The highest production was achieved under 20 psu salinity. The optimum temperature required for the maximum reproduction and shortest development time was 35 °C. The production was highest (p<.05) and development rate of A. dengizicus was shortest (p<.05) under the lowest light intensity (33.3 μmol photons/ m2/ s). Continuous light (24:0 h LD) showed positive effects on growth and production. Light regimes 24:0 h and 12:12 h LD yielded the highest total production and growth (p<.05), with highest (p<.05) survival percentage. This study demonstrated that A. dengizicus can tolerate wide range of environmental conditions and can be cultured for commercial live feed purposes as well as toxicity studies.