Muhammad Abu Bakar Siddik

FISH DIVERSITY IN THE SOUTHERN COASTAL WATERS OF BANGLADESH: PRESENT STATUS, THREATS AND CONSERVATION PERSPECTIVES

Despite the enormous anthropogenic and environmental hazards affecting wild fisheries resources, southern coastal waters are still considered one of the aquatic biodiversity hotspots in Bangladesh. Therefore, the present study was conducted to make a complete account of fishes and to assess their condition and conservation status in the rivers spread across four southern coastal districts of Bangladesh. During the study period from January to December 2014, a total of 98 species of fish were recorded belonging to 81 genera, 48 families and 13 orders. Perciforms were recorded as the most diverse fish group in terms of both number and individuals of species observed. Of the 98 species, 26.53% were listed as Locally Threatened in Bangladesh, including 11.22% species listed as Vulnerable, 10.20% as Endangered and 5.10% as Critically Endangered. Four population indices viz, Shannon–Wiener index (H), Simpson’s dominance index (D), Simpson’s index of diversity (1-D) and Margalef’s index (d) were applied to demonstrate the species diversity, richness and evenness of fish in sampling areas and their overall values were 3.54-3.70, 0.04-0.05, 0.95-0.96 and 7.48-8.67, respectively. To sustain the prospect of fisheries biodiversity in the southern coastal areas of Bangladesh, management and conservation strategies like restocking economically important fish species, establishing and maintaining fish sanctuaries, banning indiscriminate fishing and destructive fishing gears, identification and protection of the breeding and nursery grounds should be taken into consideration with utmost priority.

OVER-WINTERING GROWTH PERFORMANCE OF MIXED-SEX AND MONO-SEX NILE TILAPIA Oreochromis niloticus IN THE NORTHEASTERN BANGLADESH

The study was conducted to assess the over-wintering growth performance of mixed-sex and mono-sex male tilapia, Oreochromis niloticus. The experiment was carried out with two treatments each with three replicates for a period of 6 months from October 2012 to March 2013 in the Field Laboratory Complex, Bangladesh Agricultural University. In the first treatment (T 1 ), mixed-sex tilapia was stocked in 3 ponds with a mean initial weight of 4.80±0.18 g. In the second treatment (T 2 ), mono-sex male tilapia was stocked in another 3 ponds with a mean initial weight of 4.81±0.20 g. Fish were fed at the rate of 6% of fish body weight at the beginning of the experiments, then the feeding rates were gradually reduced to 2% for the third month and finally increased to 3% for the rest of the period. Water parameters in terms of temperature, dissolved oxygen, pH, transparency, alkalinity, ammonia and nitrite were within the range of fish farming. After 6 months of culture period, mono-sex male tilapia attained a significantly (P 0.05) difference of food conversion ratio and survival rate (%) values between the treatments. The benefit-cost ratio was calculated as 1.17 and 1.43 for mixed-sex and mono-sex male tilapia, respectively. The results suggested that it is possible to successfully culture tilapia during the winter period in Bangladesh, and the culture of mono-sex tilapia is more profitable due to its higher growth rate.

Variation in the life-history traits of a Schilbid catfish, Clupisoma garua (Hamilton, 1822) in the coastal waters of southern Bangladesh

For the first time, the present study reports the life-history traits, comprising length-frequency distribution (LFD), sex ratio (SR), length-weight relationships (LWRs), condition factors (CFs), and relative growth (WR), of Clupisoma garua in the coastal waters of Bangladesh. A total of 150 specimens ranging from 8.60 to 25.20 cm total length (TL) and 4.26 to 128.80 g body weight (BW) were collected using traditional fishing gear from August 2013 to July 2014. The overall sex ratio of males to females in the study did not differ significantly from the expected value of 1:1 (χ2 =0.96, P <0.05) but there were significant sex differences (P <0.05) in the intercepts and slopes of graphs characterizing traits in C. garua. The calculated b values for the LWRs were 2.955, 2.893 and 2.927 for males, females and combined sexes, respectively, and there was negative allometric growth in all cases (b <3). The condition factors (KA, KF, KR) and relative growth (WR) also did not differ significantly ( P <0.05) between the sexes. This study provides a useful tool for fishery specialists to evaluate the relative condition of fish and to initiate early management strategies and regulations for the sustainable management of the remaining stocks of this species in the entire coastal region of southern Bangladesh.

Stock Identification of Critically Endangered Olive Barb, Puntius sarana(Hamilton, 1822) with Emphasis on Management Implications

The study was carried out to investigate the stock identification of the olive barb, Puntius sarana (Hamilton, 1822) through morphometric characters. A total of 110 sample ranging from 10.00-16.80 cm in total length (LT) and 13.94-63.46 g in body weight (BW) were examined to assess the morphometric variation of Puntius sarana from four mighty rivers; the Padma, Meghna, Jamuna and the Halda in Bangladesh. The univariate result showed significantly variation (p<0.05) in seven morphometric characters out of 23 characters among the populations. The discriminant analysis revealed a morphological segregation among the studied populations based on the characters of length of anal base (YZ) and pre-dorsal length (LM). Discriminant function analysis (DFA) showed 55.0% of the individuals were correctly classified into the four regions on the basis of morphological characters. The first principal component (PC I) analysis elucidated 51.56% of total variation whereas PC II and PC III were 10.72% and 8.28%, respectively. The dendrogram was drawn by using morphometric data showed that the Meghna and Halda population make one cluster and the Jamuna and the Padma population form another cluster and the distance between the Padma and Meghna river population were the highest. The canonical graph also revealed all population of the Meghna and Halda were highly overlapped compare to others. The results of the present study would help monitoring the species status in Bangladesh as a bid to take appropriate management measures for its wide geographical distribution.

First record of the razorbelly scad Alepes kleinii (Bloch, 1793) (Carangidae) along the coast of Bangladesh

BackgroundThe Bay of Bengal coast, Bangladesh is a hotspot of fisheries abundance and diversity. A new species of Carangid family Alepes kleinii is recorded and described for the first time in the coastal waters of Bangladesh.ResultsA total of 29 individuals of Alepes kleinii were collected from the surveyed areas between January to March, 2016. Validation of this species was confirmed by phenotypic characteristics including body and fins colour, shape, vertical stripes, number of fin rays etc. which were found to be identical to that of the Alepes kleinii described in existing literature. The regression parameter value (b = 2.81) of the length-weight relationship (W = aLb) indicates that the Bay of Bengal provides favourable environmental conditions for the growth and development of this species.ConclusionThe discovery of the razorbelly scad in these waters provide valuable information regarding species distribution and extension, location and habitat preference. This information is prerequisite for the sound management of the coastal fisheries of Bangladesh.

Seaweed, Enteromorpha intestinalis, as a Diet for Nile Tilapia Oreochromis niloticus Fry

A 42-d feeding trial was carried out to assess the potential use of the seaweed Enteromorpha intestinalis (“gutweed”) as a food source for monosex Nile tilapia (Oreochromis niloticus) fry and to determine a maximum threshold fishmeal substitution rate. Six fish diets randomly assigned to tilapia juvenile and in triplicate were compared: replacing 0%, 10%, 20%, 30%, 40%, and 50% of fishmeal protein with a gutweed protein blend. Highest growth and cost reduction in tilapia fry production was observed in fish fed a 20% replacement diet.

Growth, biochemical response and liver health of juvenile barramundi (Lates calcarifer) fed fermented and non-fermented tuna hydrolysate as fishmeal protein replacement ingredients

Conventional aquaculture feed materials available in Australia are expensive, which has prompted the search for alternatives that would be cost-effective and locally available. The present study was undertaken in order to maximize the use of a tuna hydrolysate (TH), which was produced locally from the tuna-processing discards. The growth performance, biochemical status, antioxidant capacity and liver health of juvenile barramundi (Lates calcarifer) were assessed. Two series of isonitrogenous and isocaloric diets labelled as TH50, TH75 (non-fermented tuna hydrolysate) and FTH50, FTH75 (fermented tuna hydrolysate) were formulated to replace FM at 50% and 75%, respectively. A basal diet without the TH supplementation was used as a control. The experimental diets were fed to the triplicate groups of fish three times a day for 56 days. The results of the experiment revealed that fish fed on both fermented and non-fermented TH-containing diets significantly reduced (p < 0.05) the final body weight, weight gain and specific growth rate compared to the control. The highest apparent digestibility coefficients for dry matter, protein and lipid were obtained in the control group, and decreased with the increasing level of TH in the diets. However, the whole-body proximate compositions and the blood biochemical indices of fish were not affected by the TH inclusion in the diets. The fish fed on TH diets of TH50, FTH50 and TH75 exhibited reduced (p < 0.05) glutathione peroxidase (GPx) activity compared to the control; whereas the FTH75 exhibited no difference with the control. The excessive inclusion of TH in the diets of TH75 and FTH75 resulted in cytoplasmic vacuolization, with an increased amount of lipid accumulation, and necrosis in the liver tissue. These results indicated that the replacement of the FM protein with TH at 50% and 75% inclusion levels negatively affected the growth performance, feed utilization, and digestibility in juvenile barramundi; and it also increased the potential risk of hepatic failure in the fish. Further investigation is, therefore, required in order to optimize the TH levels in the fish diets which would be suitable for the growth of fish, as well as for maintaining the enhanced biochemical response in juvenile barramundi.

Dietary tuna hydrolysate modulates growth performance, immune response, intestinal morphology and resistance to Streptococcus iniae in juvenile barramundi, Lates calcarifer

This study investigated the effects of tuna hydrolysate (TH) inclusion in fishmeal (FM) based diets on the growth performance, innate immune response, intestinal health and resistance to Streptococcus iniae infection in juvenile barramundi, Lates calcarifer. Five isonitrogenous and isoenergetic experimental diets were prepared with TH, replacing FM at levels of 0% (control) 5%, 10%, 15% and 20%, and fed fish to apparent satiation three times daily for 8 weeks. The results showed that fish fed diets containing 5% and 10% TH had significantly higher final body weight and specific growth rate than the control. A significant reduction in blood glucose was found in fish fed 10%, 15% and 20% TH compared to those in the control whereas none of the other measured blood and serum indices were influenced by TH inclusion. Histological observation revealed a significant enhancement in goblet cell numbers in distal intestine of fish fed 5 to 10% TH in the diet. Moreover, fish fed 10% TH exhibited the highest resistance against Streptococcus iniae infection during a bacterial challenge trial. These findings therefore demonstrate that the replacement of 5 to 10% FM with TH improves growth, immune response, intestinal health and disease resistance in juvenile barramundi.

Stock Structure of the Critically Endangered Clupisoma garua (Hamilton,1822): An Investigation Based on Discriminant Analysis Approach

The stock structure of critically endangered Clupisoma garua were examined based on morphometric characters. A total of 133 specimens were collected from four rivers located in the southern coastal zone of Bangladesh. Data were subjected to principal component analysis, discriminant function analysis and univariate analysis of variance. In discriminant function analysis, plotting first and second discriminant functions explained 88.4% and 9.9% of the between-group variation for morphometric analyses indicating the existence of three morphologically differentiated groups of C. garua. The first principal component (PC1) explained 82.41% of the total variation, while PC2 explained 4.62%. The step-wise discriminant function analysis (DFA) retained six variables that significantly discriminated the populations. Using these variables, 82.0% of the original groups were classified into their correct samples and 79.70% of the cross validated groups omitting one procedure were classified into their correct samples. The result obtained from the study noticed significant differences among the populations.