Human and ecological disorder experienced in industrial settlements as a result of improper disposal of chemicals such as textile effluent calls for careful surveillance on the state of the environment. This study investigated the toxicity of textile effluent discharge using biochemical and cytogenetic responses to ascertain the acute and sub lethal effects on Clarias gariepinus. The 96 h LC50 of C. gariepinus exposed to the textile effluent was 8.203 ml L(-1). Fourteen day exposures to 1, 2, 4 and 6 ml L(-1) doses were conducted and several toxicological endpoints were evaluated. Sub lethal genotoxicity and biochemical study was also carried out for fourteen days. The genotoxicity studies utilized micronucleus test while the biochemical studies quantified serum anti-oxidant status Total Protein (TP), Catalase (CAT), Superoxide Dismutase (SOD) and Malondialdehyde (MDA) of the exposed fish. Toxicity factor indicates that the 96 h LC50 was significantly more toxic than the 24 h LC50 (p < 0.05). The textile effluent at the tested concentrations induced micronucleus and nuclear abnormalities in the peripheral blood of exposed fish. Micronucleus, notch and binucleated cell formation were significant (p < 0.05) compared to control while lobed and blebbed cells were insignificant (p < 0.05). SOD, TP and CAT significantly (p < 0.05) decreased compared to control group while MDA increased compared to control but was insignificant (p > 0.05). The results obtained from this study showed that textile effluent increase cytogenetic damage and altered anti-oxidant status in C. gariepinus. Chemicals in the effluent can be bioaccumulated and biomagnified in the aquatic organism hence affecting man.

Abstract:Egg adhesiveness has been a major problem affecting the hatchability of Clarias gariepinus. The removal of egg stickiness will improve aquaculture production through enhanced hatching rates. However, appropriate media for removal of adhesiveness in Catfish eggs is not yet well established. This study therefore, determine the optimum concentration and rinsing time of powdered milk (PM), Urea (UR) and Tannic acid (TA) for removal of adhesiveness of African catfish eggs and their effect on fertility and hatching success. Milt and eggs obtained from African Catfish broodstock of the same lineage were used for induced breeding following standard procedure. Four hundred fertilized eggs each were rinsed in the three different media at varying concentrations and exposure time using dry and wet fertilization methods. Treatment efficacy was assessed by comparing the percentage of non-stick eggs, fertilization, hatching and survival rate in the treatment groups and the control. Data were subjected to multivariate general linear model and Duncan multiple range tests at α 0 . 05 . Under the wet fertilization method eggs exposed to 10 g PM at 20 minutes gave the highest number of free eggs (87.50%) while 6g UR at 5 minutes recorded the lowest (27.09%). In dry method, 14 g PM at 20 minutes recorded the highest number of free eggs (90.00%) whereas, the lowest (47.50%) was recorded in 6g urea at one minute rinsing time. The highest number of hatchlings for PM, UR and TA were 53.26%, 33.24%, and 13.13%, respectively. The survival rate was high in all treatments except in 1.5 g TA. Eggs treated with PM solution performed best in adhesiveness removal and recorded highest percentage fertilization and hatching rate. However, more studies should be conducted to establish the appropriate media for other culture fish species.

The use of natural organic extract instead of synthetic chemicals in harvesting wild fish and eliminating unwanted aquatic biota is popular in Nigeria. This research, therefore, investigated the possibility of using the root extract of a common weed in southwestern Nigeria, named P. alliacea, in checkmating the predatory influence of nymphs of dragonfly which frequently attack fry of African mud catfish.Activity of extract was first assessed through a brine shrimp test in a 24 hr investigation before concentrations of 0.0 g/l, 0.22 g/l, 0.48 g/l, and 1.06 g/l were applied under laboratory conditions in plastic aquaria against the naiads. The 96 hr Lc 50 was 0.47 g/l obtained using probit analysis. The regression equation for the probit curve was y=3.173+3.5 (y=probit value, x=actual concentration and r=0.7=coefficient of correlation). An average of six fry and one fry were consumed by one dragonfly nymph every 96 hr at two weeks and three weeks old, respectively.

The knowledge of length-weight relationship parameters has numerous practical applications in fishery research and management. However, there is currently dearth of information on the growth pattern and state of well-being of Parachanna obscura in Eleyele Reservoir. This study therefore investigates the allometry and condition factor of P. obscura inhabiting the Eleyele Reservoir, Southwestern Nigeria. 688 specimens of P. obscura were collected from artisanal fishers' at their landing sites on a bimonthly basis for 24 months. Standard Length (SL, cm), and Body Weight (BW, g) were measured. Length-Weight Relationships (b>3 or <3-allometric; b=3-isometric), and condition factor (K) were calculated using standard formula. Data were analysed using descriptive statistics and ANOVA at α0.05. The SL and BW of P. obscura ranged from 10.6 to 39.

Propagation in fishes depends on the level of gonad maturation which could be influenced by environmental conditions. However, declining water quality due to environmental degradation has been identified as a hindrance to such ecosystem services in aquatic ecosystems. Therefore, size distribution and stages of gonad development of P. obscura in relation to physic-chemical parameters of Eleyele reservoir were studied. Samples of water and Parachanna obscura were collected monthly from five stratified sampling points and fishers catch, respectively for 24 months. Fish were grouped according to sizes (10-15.9, 16.0-19.9 and ≥ 20 cm), and gonads assessed for maturation. Relationship between reproductive indices and physic-chemical parameters were determined using Principal Component Analysis. The size-groups distributions were 10-15.9 cm (28.6%), 16.0-19.9 cm (38.7%) and ≥ 20 cm (32.7%). All the five maturation stages (I-V) were discerned in the female while only stages II-IV were observed in male samples. All the size groups showed strong associations with pH (β=0.346), ammonia (β=0.303) and temperature (β=0.161). Ovary development was significantly influenced by DO (β=0.827), TDS (β=0.777) and TS (β=0.813), while testes maturation was more influenced by temperature (β=0.626). This information will serve as guides for effective ecosystem management through the control of anthropogenic activities on this reservoir and similar water bodies to enhance resource conservation and/or sustainable management.