مجله بین المللی زیست شناسی آبزیان
سال:1396 | دوره:5 | شماره:1 |تعداد مقالات:8

The study compared the length-weight relationship and condition factor (K) of Nile tilapia(Oreochromis niloticus) in Lake Naivasha, Kenya, between the wet and dry seasons. Fish sampleswere collected monthly by gill netting from February to December 2015. A total of 372 samples ofO. niloticus were analysed. The b values in the length-weight relationships were observed as 3.077and 3.366 in the wet and dry seasons, respectively. The values of b exhibited positive allometricgrowth which were the important indication that the species was growing faster in weight than length.The K values of the fish ranged 1.18-4.1 during the wet season and 0.8-3.0 during the dry season.All mean monthly K values were found to be greater than 1, the highest being in June (2.33±0.05)and lowest in February (1.31±0.28), an indication of a healthy status and general well-being of the O. niloticus population in Lake Naivasha. The study concluded that seasonal variation has no greatinfluence in the length-weight relationship and condition factor of O. niloticus in Lake Naivasha.

This study examines the diversity and distributional patterns of benthic diatomassemblages in the upland streams of Tamiraparani River system, southern part of Western Ghats ofPeninsular India. A total of 168 benthic diatoms representing 16 orders, 32 families, and 47 generawere enumerated. Structuring of diatom community was dependent on the environmental conditionsof the respective habitats. Canonical correspondence analysis described both physical habitat qualityand water parameter gradient and factors that correlated significantly were substrate type, watertemperature, dissolved oxygen and nitrate content. Gomphonema gandhii, Cocconeis placentula andNavicula cuspidata were strongly associated with sites with embedded substrates and clear water.Diatoms could be effective in assessing physical habitat alterations in streams.

We studied the reproductive behavior and the construction of an earthen structure in thefour species of fiddler crab with reference to their habitat. Males of the Uca sindensis and U. iranicainhibit on open mudflats, construct the pillar and semidome structures at or near to the burrowsopenings. These structures perform the function to attract females, who wandering on the surfacebetween male burrows for mating as well as provide protection or hiding object against the avianpredator to mates. There were no earthen structures were observed in U. urvillie and U. annulipes, which inhibit among the vegetation. The well-marked intersexual different arrangement of mudballswas observed in U. annulipes. The earthen structures (pillar and semidome) and mudballsarrangements help courting females to assess the quality of mate as well as internal conditions of theburrow.