INTERNATIONAL JOURNAL OF AQUATIC BIOLOGY
Year:2017 | Volume:5 | Issue:1 |Papers Count: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.

Nonylphenol ethoxylate-6 (NP6EO) is widely used in industrial and domestic productsand easily detected in the environment. The toxicity and estrogenic potency of alkylphenols havebeen investigated in several studies. However, to the best of our knowledge available, acute toxicitydata about the effects of NP6EO on decapod and aquatic ecosystem in literature is yet scarce.Therefore, in this study the adult male and female whiteleg shrimp, Penaeus vannamei, were exposedto various concentrations of NP6EO (0.04, 1, 5, 25, 125, 625 mL L-1) for four days. Acute toxicitypotential of NP6EO on adult P. vannamei was assessed by calculating LC50 for different times.Median lethal concentration (LC50) of NP6EO at 96 hours was 7.017 mL L-1. The LC50 of thiscompound revealed a positive correlation between shrimp mortality and exposure periods. The dataexhibited that NP6EO was considered as "toxic" to P. vannamei and further toxicity assessment toother species is strongly recommended

This study was conducted to provide a detailed information about changes of the olfactoryorgan and telencephalon morphology in spring and fall spawning run maturing and mature Caspianlamprey, Caspiomyzon wagneri, in the Shirud River, Sothern Caspian Sea basin, Iran. A total of 71maturing and mature fish were collected during their spawning migration. The results showed thatthe thickness of the olfactory epithelium and the density of ciliated olfactory receptor cells (ORC)were lower in mature migrants. In addition, the nasal cavity, relative weight of olfactory organ andrelative telecephalon area in mature migrants were larger indicating its more sensitivity to externalqueues. Based on the results, the olfactory organ and telencephalon of maturing migrants of Caspianlamprey have not developed completely and needs a period of rest in the river to its full developmentfor spawning.

The snakehead of the family are represented 33 species from Asia of which two speciesChanna ornatipinnis and C. pulchra were recently described from Myanmar. The recent record of C. ornatipinnis from Tuivawl River, Tuivawl village in Champhai district, Mizoram, India is ofichthyological interest.

Heavy metals are among the most toxic pollutants in aquatic ecosystems. This study wasconducted to evaluate the concentration of heavy metals viz. lead, cadmium, chromium, zinc, cobalt, and copper in eight commercial fishes of Khur-e Khuran international wetland (KIW), Iran. Theresults showed that the highest concentration of heavy metals attributed to Zn as 176.5 mg g-1 dryweight in Platycephalus indicus and the lowest to Pb as 0.12 mg g-1 dry weight in Sillago sihama.Average concentrations of heavy metals in eight examined fish species were 29.15, 49.73, 1.39, 0.45, 1.43 and 1.56 mg g-1 dry weight for Cu, Zn, Cd, Pb, Co and Cr, respectively. The results also showthat measured values of most heavy metals in some examined fishes of KIW were higher than thosemaximum permissible limit (MPL) according to international standards. The high concentrations ofsome metals in some examined fishes of KIW may be due to industrial and residential activities inadjacent coast i.e. in mainland and Qeshm Island, and marine traffic

The Syrian spotted bleak, Alburnus qalilus Krupp, 1992 was described from the Nahr al-Hawaiz, the Mediterranean coastal drainage, Syria. The species differs from all other members of thegenus Alburnus in the following combination of characters: 8 branched dorsal-fin rays, 9-11branched anal-fin rays, 43-47 scales in the lateral line and 9-11 gill rakers on the lower limb of thefirst gill arch. In the present study, the occurrence of this species is reported for the first time fromthe Turkish parts of the Orontes river basin in Kilis, Gaziantep and Hatay provinces. Our new dataindicate that the home range of this species has been increased towards the Turkish parts of theOrontes river basin.