Haematological and biochemical responses of juvenile malabar blood snapper (Lutjanus malabaricus Bloch & Schneider, 1801) exposed to different rearing temperatures and diets

This study is conducted to examine the impacts of different rearing temperature and diet variation on haematological and serum biochemical parameters on the juvenile Lutjanus malabaricus, a commercially important fish species in Malaysia. Fish (16-18 cm) were divided into eight treatments (4 temperatures × 2 diets) each with three replicates of five juveniles each. Fish were subjected to four different rearing temperatures (22, 26, 30 and 34°C) and fed with a commercial pellet and a natural shrimp diet. After 30 days of experimental period, blood samples were collected and transferred into two different tubes from each sample: One containing EDTA as an anticoagulant agent and the other without EDTA for serum collection. All the haematological and biochemical parameters in all the treatments were within the normal range. Changing temperature and diet led to a significant change (p0.05). The fish reared at 26°C and 30°C had significantly higher values than those reared at 22°C and 34°C (p<0.05). Total protein (TP), albumin (ALB), albumin/globin ration (A/G ratio), alkaline phosphatase (AP), aspartate aminotransferase (AST) and alanine transaminase (ALT) level were also significantly increased at 30°C and 26°C compared to that of 34°C and 22°C. Globulin (GLB) level showed the opposite trend. In all the cases the performances were higher in shrimp diet than pellet diet. It is suggested that these physiological parameters can be conveniently employed as health monitoring tools in fish culture practices

Length-weight relationships and condition factors of mono- and mixed-sex Nile tilapia (Oreochromis niloticus) in open water cage culture system

The current study compared the length-weight relationships and condition factors in mono- and mixed-sex Nile tilapia (Oreochromis niloticus). The trial lasted for 91 days and included two treatments with five replications for each, all with the same stocking density. During the study period, 20 randomly selected fish individuals were measured and recorded from each cage every two weeks. The observed growth trend was allometric, with no significant difference in the mean exponential values (b), 2.696 and 2.65 for mono and mixed-sex tilapia respectively. There was a significant difference in final weight gain between monosex (171.58±7.39 g) and mixed-sex (149.09±4.14 g) tilapia. There was no significant difference in final length between monosex (19.80±0.42 cm) and mixed-sex (19.80±0.42 cm) tilapia. Moreover, the mean correlation coefficient (r2) of both groups was positive. The Fulton condition factor (K) also varies from 0.700 to 1.000 (monosex) and 1.000 to 1.010 (mixed-sex). The relative condition factor (Kn) for monosex and mixed-sex tilapia ranged from 1.96 to 2.222 and 2.092 to 2.35 respectively, indicated good aquaculture conditions. The present findings will attract fish farmers to mixed-sex tilapia culture by allowing them to lessen hormone administration and expected to boost national fish production through open water cage aquaculture

Effects of sodium nitrate on the growth and proximate composition of the indigenous marine microalgae Tetraselmis chuii (Butcher, 1959)

Nitrogenisoneofthefundamentalnutrientsforalgalgrowth,underpinningthemicroalgalbio-chemical composition. Therefore, this study compared the growth and proximate compositions of Tetraselmis chuii (Butcher, 1959), cultured in different nitrate (NaNO3) concentrations (25, 50, 100, 200 and 500 mg L-1). Thus, the cell density, optical density, specific growth rate and division rate of T.chuiiweremeasureddaily.Furthermore,proteinandcarbohydratecontentswerealsodeter-mined in the stationary phase. The results showed that T. chuii cultivated in a NaNO3 concentration of500mgL-1hadsignificantly(p lt;0.05)highergrowthintermsofcelldensity,biomass,opticaldensity, specific growth rate and division rates compared with other concentrations. Likewise, pro-tein content was also significantly higher under the NaNO3 concentration of 500 mg L-1, whereas significantly (p lt;0.05) higher carbohydrate content was found at 25 mg L-1 NaNO3 compared with the other concentrations, showing a contrary trend between protein and carbohydrate concentra-tions, respectively. Since the primary focus has been on improving the quality of microalgal bio-mass in order to develop novel processes and products, this is the first study to use higher concen-trationsofmodifiednitrateonT.chuiiisolatedfromthecoastalareaofBangladesh.Thustheindigenous marine T. chuii had significantly utilised NaNO3 concentrations with higher growth and proximatecontentsinthisstudy.However,furtherstudyisneededonmicroalgalgeneticsandmetabolic engineering to create a new molecular era of the indigenous marine microalgae isolated from the coastal water of Bengal

Seasonal dynamics of stomach contents, trophic level, length-weight relationship and condition factor of Mystus bleekeri (Day, 1877)

The Asian catfish Mystus bleekeri is a popular food fish along with favored as an ornamental fish in Bangladesh. Till now detailed report on stomach contents, trophic level, length-weight relationship and condition factor of this fish species in the agro-climatic context of Bangladesh is lacking. Hence, the aims of this study were to describe the stomach content, trophic level, length-weight relationship (LWR) and condition factors of Mystus bleekeri collected from Dekhar Haor, Sylhet, Bangladesh from July 2017 to June 2018. A total of 600 specimens ranging from 6.9-24.6 cm total length (TL) and 5.7-72.4 g body weight (BW) was analyzed in this study. Stomach content analysis showed that the fish fed mostly on Mollusca with a frequency of occurrence (fo : 25.36%) and worms (fo : 21.68%), followed by plant matters (fo : 3.32%), Cladocerana (fo : 1.18%), Copepoda (fo : 0.95%), and Teleostei (fo : 0.36%). The estimated mean trophic level (TROPH) ranged from 2.35±0.13 in December to 3.02±0.23 in August, indicating that they are opportunistic feeder. The LWR analysis showed negative allometric growth (b<3) throughout the year. The values of the exponent b in the LWR (W=aLb ) vary between 1.474 and 2.490. The mean K value was significantly higher in October indicating the heavier weight and better condition of the fish (P<0.05). The data obtained from this study would be useful to introduce sustainable management of Mystus bleekeri not only in Dekhar Haor but also in other inland waters of Bangladesh

Biological and Reproductive Indices of Mystus bleekeri (Day, 1877) in Open Water Body (Dekhar Haor) of Bangladesh

Some biological and reproductive aspects of the Mystus bleekeri from Dekhar Haor were investi-gated. From the commercial catches, a total of 600 sample collections were performed on a month-ly basis from July 2017 to June 2018. Total length (TL, cm), body weight (W, g) and individual’s sex were identified between 216 male (36%) and 384 female (64%) fish (ratio 1.00: 1.78). Mean TL and Wofsampleswere14.85±3.38cmand27.54±15.76g,respectively.TheTLofmaleandfemaleranged from 6.9-21.3 and 7.80-24.60 cm, respectively; and W ranged from 5.3-63.3 and 6.70-76.40 g,respectively.Inlength–weightrelationshipofthisfishdepictedanegativeallometricgrowth(b=2.408) with a condition factor (Kn) of 1.04±0.11. Fish of 16.00-16.90 and 10.00-10.90 cm length groups demonstrated the highest (1.45±0.23) and lowest (0.89±0.18) Kn values, respectively which wassignificantlyvariedamongdifferentlengthgroups.MonthlystudyofgonadosomaticindexshowedtwopeaksinthemonthofMay-JuneandNovemberforbothsexes.Theresultsofthisstudy provide baseline data on some biological aspects of M. bleekeri, which would be useful in predicting the responses of M. bleekeri populations in Dekhar Haor

High levels of genetic variability and differentiation in hilsa shad, Tenualosa ilisha (Clupeidae, Clupeiformes) populations revealed by PCR-RFLP analysis of the mitochondrial DNA D-loop region

The hilsa shad, Tenualosa ilisha (Clupeidae, Clupeiformes) is an important anadromous clupeid species from the Western division of the Indo-Pacific region. It constitutes the largest single fishable species in Bangladesh. Information on genetic variability and population structure is very important for both management and conservation purposes. Past reports on the population structure of T. ilisha involving morphometric, allozyme and RAPD analyses are contradictory. We examined genetic variability and divergence in two riverine (the Jamuna and the Meghna), two estuarine (Kuakata and Sundarbans) and one marine (Cox's Bazar) populations of T. ilisha by applying PCR-RFLP analysis of the mtDNA D-loop region. The amplified PCR products were restricted with four restriction enzymes namely, XbaI, EcoRI, EcoRV, and HaeIII. High levels of haplotype and gene diversity within and significant differentiations among, populations of T. ilisha were observed in this study. Significant FST values indicated differentiation among the river, estuary and marine populations. The UPGMA dendrogram based on genetic distance resulted in two major clusters, although, these were subsequently divided into three, corresponding to the riverine, estuarine and marine populations. The study underlines the usefulness of RFLP of mtDNA D-loop region as molecular markers, and detected at least two differentiated populations of T. ilisha in Bangladesh waters

Status and Decline Causes of Fish Diversity of Bhawal Beel, Bangladesh

Beel is one of the ancient types and obviously a fascinating one due to its biodiversity and ecological importance in local and national perspective of Bangladesh. The Bhawal beel is one of important beels and excellent habitat for small indigenous species (SIS). The present status and decline causes of Bhawal beel was studied from March 2016 to February 2017. Data collection was carried out from four villages of Achim union under Fulbaria upazila. Questionnaire Interview (QI), Focus Group Discussion (FGD) and cross-check Interview were done to obtain data related to status and decline causes of fishes from the fishermen and resource person. A total of 56 species of fish including prawn under 10 orders and 23 families were recorded from thebeel. Cypriniformes (33.93%) was the most dominant order followed by Siluriformes (21.43%), Perciformes (19.65%), Channiformes (7.14%), Synbranchiformes (7.14%), Decapoda (3.58%), Cyprinodontiformes (1.78%), Osteoglossiformes (1.78%), Beloniformes (1.78%) and Tetraodontiformes (1.78%). Among the recorded families Cyprinidae was the most dominant family contributing 17 species. The availability status of observed species were remarked in four categories and obtained as available (44.64%), seasonal (19.64%), rare (16.08%) and very rare (19.64%). Decline causes like overfishing, use of illegal fishing gear, siltation, katha fishing, and abstraction of water for irrigation, catching of fry and brood fishes, lack of connection of beel with Banar river and absence of proper beel management policy were observed as major threats for fish diversity.&nbsp; About 13species were found threatened (1 critically endangered, 5 endangered and 7 vulnerable) which may extinct in near future due to proper management of the beel fishery. The present study recommends minimizing of all these impediments. Besides Community Based Fisheries Management (CBFM) and beel nurseryis essential to save the valuable fish diversity of Bhawal Beel on which local livelihood depends. &nbsp

Temperature and diet effect on the pepsin enzyme activities, digestive somatic index and relative gut length of Malabar blood snapper (Lutjanus malabaricus Bloch & Schneider, 1801)

An integrated experiment was performed on juvenile Malabar blood snapper (Lutjanus malabaricus) to investigate the effect of temperature and diet in their pepsin activities in relation with digestive somatic index (IDS) and relative gut length (RGL). One hundred twenty L. malabaricus juvenile (13–15 cm) were equally distributed among four exposed temperature treatments (22, 26, 30 and 34 °C) representing their seasonal range and to account for end of century predicted temperatures, and two diets as commercial pellet and natural shrimp. After 7 days of acclimation period fish were reared for 30 days in twenty four 400 l glass aquaria at a stocking density of 5 fish tank−1. All treatments were three replications. The result showed that, IDS and RGL gradually decreased with increasing temperature up to 30 °C and again increase at 34 °C. And the values were also higher in pellet feeding fish than shrimp feeding fish at all the temperatures. Alternatively, in pepsin activity, an increased activity was seen between 26 °C to 30 °C and this activity was significantly higher than the 22 °C and 34 °C (P < 0.05). In general, highest pepsin activity was observed among fish which fed on a natural shrimp diet reared at temperature 30 °C (5.47 ± 1.60 U mg protein−1), followed by those at 26, 34 and 22 °C (P < 0.05) at both diet however, no mortalities were observed. These results could be used as a basis for selecting a suitable diet for maximizing the growth and sustainable aquaculture coping with global warming

Fish Culture Practice and Socio Economic Status in Northern Middle Part of Bangladesh

The present study was carried out in Bhaluka upazilla, the northern middle part of Bangladesh to observe the culture technique of fish culture using of supplementary feeds and socio-economic condition of the fish farm owners. Data were collected from 39 fish farms in Bhaluka upazilla during the period from September 2010 to August 2011. Most of the studied farm owners carried out polyculture system and culture, mostly carps (Indian major carps and exotic carps), pangus and tilapia using supplementary feeds. The feeding rate varied from 1-7% of body weight of fish with frequency 1-3 times/day. The highest production was recorded as 56,810 kg/ha/yr using company feed and the lowest production was recorded as 14,210 kg/ha/yr with an average production of 34,350 kg/ha/yr. The average production of 23,520 kg/ha/yr was recorded (farm made feed). Most of the farmers did not use fertilizer and manure in their ponds, but in winter season sometimes they used poultry litter to avoid high priced feed. The overall management practice was not smoothly developed in the monoculture and polyculture farms. It may be concluded that we have to reduce all of the constraints of management practices of aquaculture to achieve sustainable growth in future aquaculture of Bangladesh.&nbsp; &nbsp