Mohammad Mustafizur Rahman

Effects of food type on diel behaviours of common carp Cyprinus carpio in simulated aquaculture pond conditions

In order to better understand behaviour patterns of common carp Cyprinus carpio in aquaculture ponds, their diel grazing, swimming, resting and schooling behaviours were observed in six 1 m(2) tanks under simulated pond conditions. Each tank was fertilized to stimulate natural food production before starting experiments, and then stocked with three C. carpio. Fish behaviours were compared among three treatments: (1) tanks with plankton only, (2) tanks with plankton and benthic macroinvertebrates and (3) tanks with plankton, benthic macroinvertebrates and artificial feed. Overall C. carpio grazed more frequently during daytime than at night and exhibited the reverse pattern for non-feeding swimming behaviour. A significant negative relationship (r(2) = 0.99, P < 0.01, n = 48) was observed between total per cent grazing time and total per cent swimming time. Fish dispersed to graze individually during daytime but schooled at night and did not display any agonistic behaviours. Diel variations in the vertical swimming behaviour of C. carpio were related to food types available. In tanks containing plankton only, fish grazed in the water column, whereas when benthic macroinvertebrates were present, they spent more time near the tank bottom. Resting behaviour was only seen in tanks with artificial feed and even then was rare (2-5% of total time). Results suggest that C. carpio growth and feed utilization efficiency in semi-intensive aquaculture systems could be optimized by using a combination of plankton, benthic macroinvertebrates and artificial feed, and feeding fish twice per day (at c. 0730 and c. 1630 hours).

Threatened fishes of the world: Pangasius pangasius Hamilton-Buchanan, 1822 (Pangasiidae)

Common names: Jambal, Pangas, Pariasi, Ponnga, Yellowtail catfish. Conservation status: Critically endangered (IUCN Bangladesh 2000). Importance: Previously commercially important for fisheries and aquaculture on the Indian subcontinent and Myanmar. It is a very desirable gamefish and highly valued food fish. Identification: D 1/7, P1 1/12, P2 6, A 3–4/26– 29, vertebrae 42–45. Body is elongateded and compressed. Mouth subterminal; two palatine and two vomarine tooth rows; gill rackers on first arch 23–28. The caudal fin is deeply forked and bright yellow in adults. The dorsal spines are strong, slightly serrated anteriorly and denticulated posteriorly. Pelvic fin origins below the dorsal (Roberts and Vidthayanon 1991). Distributions: Tropical (23–28°C; 35°–8°N). Large rivers and estuaries of the Indian subcontinent and Myanmar (Roberts and Vidthayanon 1991). Abundance: Previously abundant in Ganges and Brahmaputra rivers, but populations have declined seriously (Prasad 1994; IUCN Bangladesh 2000). No recent population estimates are available. Habitat and ecology: Inhabits streams, lakes, estuaries, and mangrove swamps with hard bottoms or sea grasses; feeds on plants, shrimps, insects, mollusks and worms. Reproduction: July–October (Rahman 1992). Does not breed in ponds and therefore difficult to culture. Threats: Over-exploitation, destruction of habitats and breeding grounds from river damming, natural disasters and water pollution. Conservation action: Artificial propagation has been successful in Bangladesh (Khan and Mollah 2004). Conservation recommendations: A survey should be conducted to determine the current abundance, distribution and ecology of this species, and to identify reasons of Environ Biol Fish (2009) 84:315–316 DOI 10.1007/s10641-008-9422-y

Role of common carp (Cyprinus carpio) in aquaculture production systems

Common carp (Cyprinus carpio) is considered to be a very important aquaculture species in many Asian and some European countries. It affects the aerobic decomposition of organic matter and nutrient availability in the water column via bioturbation of benthic sediment during feeding on benthic organisms. If the density of common carp is not excessive, an increase in nutrient availability may enhance photosynthesis and plankton production, whereas if it is excessive, it causes dramatic ecological disruption at both the community and ecosystem levels by changing the abiotic properties of the water. Therefore, the density of common carp is a very important factor that has a great effect on the aquatic ecosystem. The critical density of common carp largely depends on its habitat. In polyculture ponds, water quality, natural food resources and fish growth are strongly affected when the density of common carp approaches more than about 1000 kg ha−1. The critical density can be doubled if artificial feed is supplied to the carp. When its preferred food is not sufficient, the common carp switches to less preferred food and changes its behaviour and feeding niche. These factors make common carp a potential candidate not only for monoculture but also for polyculture ponds. This article reviews the role of common carp on the aquatic ecosystem, and the production and behaviour of fish in aquaculture production systems.

Effect of cholymbi on growth, proximate composition, and digestive enzyme activity of fingerlings of Long whiskered catfish, Mystus gulio (actinopterygii: siluriformes: bagridae)

Background. Long whiskered catfish, Mystus gulio (Hamilton, 1822), enjoys a high consumer preference and market demand in many Asian countries including India. However, the growth of this fish is very slow under normal aquaculture conditions. The non-hormonal growth promoter—cholymbi—which contains minerals and the essential amino acids lysine and methionine, is widely used in livestock and poultry as a feed additive to improve growth and survival. Supplementing feed with cholymbi may increase the growth and survival of Mystus gulio. Materials and methods. A feeding trial was conducted to determine the effect of dietary cholymbi supplementation on growth, survival, and feed conversion ratio of long whiskered catfish fingerlings. Four isoproteic diets (crude protein 37%) were formulated to incorporate cholymbi at 0%, 0.25%, 0.50%, and 0.75% diet. The diets were fed to triplicate groups of fish twice daily to supply 5% of the total body weight per day for 120 days. Water quality parameters were maintained within the range suitable for catfish growth. Results. Weight gain (WG), protein efficiency ratio (PER) and feed conversion ratio (FCR) were all affected by diet (P < 0.01, 0.001, and 0.001, respectively). The group fed the 0.50% cholymbi diet had the highest WG and PER and the lowest FCR, although not significantly different from the group fed the 0.25% cholymbi diet. There was no significant difference (P > 0.05) in carcass proximate composition of catfish fed diets containing these different levels of cholymbi. Gut protease, amylase, and lipase activities were stimulated by dietary inclusion of cholymbi at all levels compared to control. Conclusion. As cholymbi is a newly introduced dietary supplement for fish, more research is needed to optimize its supplementation to improve growth, PER, FCR, and survival of long whiskered catfish. Until then, a diet with 0.50% cholymbi can be recommended to improve the aquaculture production of this species.

Coastal water quality of Tioman Island: effects of human activity and the distance from shoreline

A study was conducted to know the (i) effect of anthropogenic activity and (ii) effects of distance from shoreline on the coastal water quality of Tioman Island, Malaysia. This study was a part of marine expedition conducted on 4 July 2012 to understand coral diversity and distribution around coastal water of Tioman Island. A series of physicochemical parameters namely temperature, dissolved oxygen (DO), pH, salinity, transparency, total suspended solids, nitrate, ammonia, phosphate phosphorus, and silicate were determined in this study. A total of 16 different study sites (stations 1‐16) were selected in the coastal water around the Tioman Island. Half of the study sites was located within 1 km from the shoreline and other half was located approximately 6 km away from the shoreline. Some study sites are characterized by no human activity, while some sites are characterized by diving activities. A few study sites are characterized with both diving activity and near residential area. The overall mean values of different water quality parameters recorded in the all sampling stations were temperature 27.98 ± 0.40˚C, pH 8.34 ± 0.02, DO 6.92 ± 0.43 (mg l �1 ), salinity 33.54 ± 0.11 pss, TSS 0.39 ± 0.03 g l �1 , nitrate 0.85 ± 0.55 μM, ammonia 1.89 ± 0.56 μM, phosphate 0.16 ± 0.09 μM, and silicate 2.62 ± 0.76 μM. Temperature, DO, transparency, salinity, and ammonia were significantly affected by anthropogenic activity, while anthropogenic activity had no significant effect on pH, total suspended solids, nitrate, and phosphate. No significant difference was observed between the water quality of 1 km from shoreline and 6 km away from shoreline. Good and careful management by the authorities of this island may save the biodiversity and beauty of the coastal water of Tioman Island. Therefore, a balance between human activity and conservation of biodiversity on the coastal water of Tioman Island is needed.

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.

Seasonal variations in the structure of copepod assemblages in tropical marine and estuarine waters, Coleroon, south-east India

A twelve-month investigation was undertaken on how copepod community structure varied in relation to environmental factors in the Coleroon estuary, south-east India. Sampling was monthly, from Station 1 in the sea to Station 4 in the Vettar backwaters. Canonical correspondence analysis (CCA) was applied to elucidate the environmental factors affecting the copepod community. A total of 104 copepod species in 38 genera and 26 families were recorded, with the Calanoids, Acartia erythraea and Oithona brevicornis being the most dominant. At all four stations, both these species loaded near the intercept of CCA axes 1 and 2, perhaps reflecting that they were autochthonous. Most species occurred in distinct seasonal patterns. Abundances ranged from 13x10(3) to 215x10(3) (ind.m(-3)). Coleroon waters showed high diversity (bits/ind.), from 5.29 at Station 3 to 4.97 at Station 4. Abundance correlated positively with temperature and salinity and negatively with rainfall, dissolved oxygen concentration (DO) and pH. Species diversity correlated strongly with abundance (P<0.01). Abundance and diversity were highest during the summer, and both correlated positively with salinity. Temperatures (air and water), salinity, pH and DO varied in the ranges 26-36 degrees C, 25-34.2 degrees C, 9-38, 7.0-8.7 and 3.0-6.8mll(-1), respectively. Nitrate, nitrite, phosphate and silicate (mu M) varied in the ranges: 4.7-64.5, 0.4-14.1, 0.2-12.9 and 9.3-148, respectively.

DNA Barcoding and Molecular Phylogeny of Indigenous Bacteria in Fishes from a Tropical Tidal River in Malaysia

DNA barcoding along with molecular phylogeny can be used for taxonomic identification, characterization, discovery of species and understanding molecular relationships especially in terms of species divergence. Thus, they facilitate biodiversity studies. Some studies have addressed DNA barcoding of bacterial samples from various sources. Unfortunately, the DNA barcoding of fish bacterial diversity has not been studied especially in the tropical tidal river. Therefore, a study was conducted to (1) identify the observed bacterial isolates by comparing the partial sequence from an unknown sample to a collection of sequences from known reference samples, (2) know the taxonomic and phylogenetic identity of identified bacteria in fish and (3) know the abundance of fish bacteria in the Kuantan River. For this study, three commercially important fish namely Pristipomoides filamentosus, Cyclocheilichthys apogon and Labiobarbus festivus were captured with gill nets from the Kuantan River, Malaysia. Bacteria from skin, gill and gut in fish were cultured at 35 °C for 24 h in both nutrient and marine agar. Bacterial DNA was extracted using a Bacterial Genomic DNA Isolation Kit following manufacturer’s specifications. Isolated DNA was quantified in NanoDrop 2000v and gel eluded in 1.5% agarose gel and visualized under a gel visualizer. PCR products were outsource sequenced at First BASE Laboratories Sdn Bhd using an ABI sequencer by the Sanger sequencing method. Sequences were trimmed using sequence scanner 2.0 V. The aligned sequences were inspected by the eye and edited to remove ambiguities based on PHRED scores and the chromatogram. Fully aligned sequences were subjected to BLAST for nucleotide similarity search against 16S rRNA database. The best matched species were selected based on BLAST results and the lowest genetic distance between the known and unknown nucleotides. Genetic distances (sequence divergences) were calculated using the K2P (Kimura two parameter) distance model. Neighbour-joining (NJ) trees of K2P distances were created to provide a graphic representation of the patterning of divergence between species. This method identified a total of 11 fish bacteria, which are taxonomically classified into Enterobacteriales, Pseudomonadales, Actinomycetales and Bacillales. The range of pairwise genetic distances between species of Enterobacteriales was lower than Bacillales. Similarly, the within group mean genetic distance of Enterobacteriales (0.010) was lower than that of Bacillales (0.055). These results indicate that the identified bacterial species under Enterobacteriales are more closely related than the bacteria species under Bacillales. The mean genetic distances between groups were genetically almost equally close, which was confirmed by the overall mean diversity. Out of 11 species, 7 were identified as Cyclocheilichthys apogon, 8 as Labiobarbus festivus and 7 as Pristipomoides filamentosus. The overall mean bacterial abundance (CFU/g) was higher in C. apogon (6.68 × 103) compared to those in L. festivus (5.12 × 103) and P. filamentosus (5.20 × 103). Overall, the highest bacterial abundances were observed in fish gut (6.62 × 103), followed by fish gill (5.78 × 103) and fish skin (4.60 × 103).