Intraspecific morphometric diversity of barramundi (Lates calcariferBloch, 1790) in the waters of southern Bangladesh

A total of 160 barramundi's (Lates calcarifer Bloch, 1790) sampled from four rivers (Tentulia, Balaswar, Bakkhali, and Andarmanik) along the southern coastal region of Bangladesh were investigated in terms of morphometric characters to reveal the intraspecific variation. Twenty-five morphometric measurements were extracted using the conventional method and subjected to multivariate analyses (i.e., principal component analysis (PCA), discriminate function analysis (DFA), cluster analysis (CA)) to distinguish individuals from different rivers. The result demonstrated that twenty-two out of 25 measurements was statistically significant (Univariate ANOVA) among all four populations. PCA analysis of morphometric characters resulted in two principal components, PC I and PCⅡ which accounted for 79.25% and 4.28% of the total data variance. PC I-PC Ⅱ plot explained 83.53% of total variance differentiated the population of L. calcarifer into two groups. Discriminate analysis correctly classified about 88.1% of the examined fish into the four areas. The UPGMA dendrogram showed that Bakkhali populations were the most morphologically different populations in comparison to other populations, while Andarmanik and Balaswar populations were very close to each other. The strong morphometric variation between Bakkhali and Tentulia, Andarmanik and Balaswar was observed in the present study, suggested the evidence of the separate stock population of barramundi in these locations, which might require distinct stock management strategies for resource sustainability in the waters of southern Bangladesh. However, if these findings are supported by further molecular markers and geometric morphometry, this would be a strong indication of different stocks of this population in the four rivers of southern Bangladesh.

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(W_R),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 dif fer significantly from the expected value of 1:1(χ~2=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 bvalues 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(K_A,K_F,K_R)and relative growth(W R)also did not differ significantly(P<0.05)between the sexes.This study provides a useful tool for fi shery 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.

Coastal set bagnet fishery in the Payra river,Bangladesh and its impact on fisheries and biodiversity

Objective:To assess the catch composition and seasonal variation in catch of set bagnet fishery from the coastal Payra river,to understand the importance and impact of set bagnet fishery on biodiversity and fisheries,and to find out feasible strategies to reduce the negative impact of set bagnet fishery.Methods:The research was conducted with selection of research area,preparation of gear survey and catch assessment form,sample collection,laboratory analysis and selection of analytical methods to achieve the objectives of the study.Results:A total of 52 species belonging to 23 families were recorded from set bagnet in the Payra river.Most important commercial fishes and their annual catch by set bagnet in the study area were 51.03 MT Ilish(Tenualosa ilisha),8.83 MT Rita(Rita rita),6.92 MT Air(Sperata aor),4.72 MT Chital(Chitala chitala),2.03 MT Boal(Wallago attu),1.84 MT Baghair(Bagarius bagarius),3.35 MT Foli(Notopterus notopterus)and 13.46 MT Golda chingri(Macrobrachium rosenbergii).All these species were mostly caught at initial stages of their life cycle,which usually move with the tidal current.Conclusions:Study suggested that set bagnet should be restricted to allowable limit with strong monitoring system for the protection and conservation of valuable fish species in the coastal areas of Bangladesh.