Morphological relationships, growth patterns and some aspects of reproductive biology of Sind Danio Devario devario (Hamilton 1822)

This study examined the morphological relationships, growth population factors and reproductive biology of Devario devario collected from the Atrai River of Dinajpur, Bangladesh, for sustainable management and conservation aspects. The length-weight relationships (LWRs) commonly indicated the isometric growth. The Fulton’s condition factor (CFf) and relative body weight (BWr) varied across sexes. A positive correlation was found in length-length relationships (LLRs); among total length (TL), standard length, head length and fork length. The asymptotic lengths were 7.5, 7.2 and 7.5 cm, with growth rates of 0.78‒1.8, 0.6‒3.4 and 1.8‒3.6 year–1 while total mortality was 1.22‒3.06, 0.97‒7.07 and 3.70‒6.09 year–1; fishing mortality was –0.87 to –1.04, –0.97 to 1.09 and –0.05 to –0.23 year–1; natural mortality was 2.26–3.93, 1.94–5.98 and 3.93–6.14 year–1 for female, male and combined sexes respectively. The highest probability of capture (L50) was 5.74‒6.15 cm. The gonado-somatic index ranged from 32.75±1.82 to 44.12±2.73, with a peak in April to May. Fecundity was recorded from 3253±289 to 4831±342, with a significant correlation among TL, BW, gonad length (GL) and gonad weight (GW). These initial findings on D. devario will serve as the basis for future research and management

Prebiotic potential of Azolla pinnata (R.Br.) and dietary inclusion effect of pulverised azolla on the growth performance of milkfish fingerlings

The growth of the aquaculture sector leads to a demand for sustainable feed ingredients. Prebiotics are potential sustainable feed ingredients that can promote the improved performance of aquaculture species without the use of antimicrobials. This study investigated the potential of Azolla pinnata as a candidate prebiotic source. Prebiotic characteristics and dietary effect of commercial diet (CD) with varying pulverised azolla (PA) inclusion was evaluated. Results showed that PA (9.40% moisture) constitutes around 16.1% ash, 22.3% crude fibre, 20.9% crude protein, 1.7% crude fat and 29.6% nitrogen-free extract. Crude xylan and cellulose content of PA were 13.7% and 12.6% dry matter (DM) respectively. Growth of Lactobacillus rhamnosus in PA-supplemented MRS broth remarkably improved after 4 to 6 hours of incubation. Feeding trials results revealed that PA inclusion had no adverse effect on average survival of milkfish fingerlings, albeit significant improvement (p < 0.01) was noted in group fed with 2% PA-replaced CD in terms of the total weight gain (119.9%), specific growth rate (2.62% day–1) and feed efficiency (79.9%). The present study demonstrated the prebiotic activity of PA, as well as its potential use as dietary feed component for improved growth and feed efficiency of cultured milkfish

A study on the diversity, marketing and conservation status of different aquatic food fauna in Kokrajhar, Assam, India

Kokrajhar district of Assam in North-eastern India has several natural water resources that harness a variety of aquatic fauna. Understanding the aquatic biodiversity is vital for the sustainable development of fisheries and aquaculture expansion. The present study aims to record the diversity and marketing of aquatic food faunal resources in Kokrajhar, Assam. Surveys were conducted in three village markets and two town markets of Kokrajhar. Altogether, 64 finfish, 6 shellfish and 4 aquatic insect species were recorded. The abundant presence of diverse small indigenous fish species indicates the potential for the aquaculture expansion of these species in the region. Majority of the species (77%) were found to be Least Concern, whereas, 5, 3 and 1 species were Near Threatened, Vulnerable and Endangered respectively as per IUCN Redlist database. A higher demand and market price were observed for all locally captured species. This study has highlighted the rich aquatic food faunal biodiversity of Kokrajhar and the socio-economic condition of the local fishers. The information from this study may be useful in the sustainable development of fisheries and aquaculture in the region

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

Traditional fishing methods practiced by Ao and Sumi tribes in Dikhu River of Nagaland, India

Traditional fishing knowledge dates back to the early fish catching techniques passed down from forefathers in most of the Naga communities, Nagaland. Traditional fishing is mainly practiced for household consumption and is considered less intensive than industrial fishing practices, which can negatively impact riverine sustainability. However, there is a risk of loss of traditional knowledge in recent times. Hence, an effort was made to comprehend and document the indigenous traditional knowledge associated with fishing practices utilized by the Ao and Sumi tribal communities residing along the banks of Dikhu River. The diverse array of traditional fishing equipment and techniques employed has been categorised based on their specific functions, resulting in the documentation of three types of fishing gears, four fishing accessories, one fishing craft and three other types of fishing techniques. However, in some regions, use of detrimental fishing like dynamites and harsh chemicals were encountered. The results indicate that local fishers continue to rely on indigenous fishing practices for sustenance, and the majority of traditional fishing gears are constructed using locally available eco-friendly materials such as bamboo, wooden poles and cotton twine. The information obtained in this study can be preserved and implemented in contributing better resource management

The morphometric, meristic and genetic characteristics of European sprat (Sprattus sprattus) in the Black Sea

The European sprat (Sprattus sprattus) represents the unit stock shared among the Black Sea countries. It has a key role in the Black Sea ecosystem and is determined by its importance from both a commercial and an ecological point of view. Up to now, there are few studies on the meristic, morphometric and genetic characteristics of this species. In this study, the species were specified and studied for meristic, morphometric and genetic characteristics. Mitochondrial gene regions which 16S rRNA and cytochrome c oxidase subunit I (COI), were studied and compared with some of the family Clupeidae species in the National Center for Biotechnology Information (NCBI) and the phylogenetic relationship was examined. A total of 14 haplotypes were determined for the mitochondrial COI gene region and 3 haplotypes were determined for the 16S rRNA gene region. This study will contribute to the sustainable management of this species as well as be a basis for future studies

Occurrence record and range extension of Pomadasys andamanensis McKay & Satapoomin, 1994 (Heamulidae: Haemulinae) from Great Nicobar Island, India

Present study reports the occurrence of Andaman grunt, Pomadasys andamanensis McKay & Satapoomin, 1994 for the first time from Indian waters based on one specimen (standard length 156.27 mm) collected from Great Nicobar Island, Andaman and Nicobar Island. This finding represents a new addition to the grunt fish fauna of Andaman and Nicobar Island, India. The species is distinguished from its congeners by having four separated longitudinal black stripes on the dorsal half of the body. The detailed morphological features of P. andamanensis are provided and compared with its previous records. Description and figures of the species are provided herewith along the morphometric measurements and meristic counts

Determining overwintering performance and economic viability of monosex tilapia fingerling production in hapa cum cage aquaculture system for Bangladesh's haor fishers

Ensuring a consistent supply of uniformly sized fingerlings for tilapia cage aquaculture in Bangladesh's poses a significant challenge. This study assessed overwintering growth performance and economic viability of monosex tilapia fingerling production in haor waters. Nine hapas, each inside a designated treatment cage, were stocked with T1 (200), T2 (250) and T3 (300) tilapia fry, averaging 1.25±0.25 g, per m³ for 90 days. The most successful treatment continued for two subsequent crops over two years for economic viability assessment. Average final body weight gain was the highest at the lowest stocking density (T1, 58.86±7.23 g), but the most desirable biomass gain (222 kg cage⁻¹) occurred at medium stocking density (T2). Beyond biomass gain, T2 exhibited superior profitability, with 26% and 30% profitability in the second and third crops respectively, over total costs. In conclusion, overwintering tilapia fingerling production in the hapa-cum-cage system at a stocking density of 250 m⁻³ proved more profitable and sustainable than other treatments, offering a viable income-generating option for resource-poor haor fishers

Factors affecting abundance and primary productivity of phytoplankton in a wetland ecosystem of Bangladesh

Wetlands are the most productive, economically important and hydrologically variable ecosystems. In this study, the abundance of phytoplankton and its primary productivity were evaluated in Dingapota Haor of Bangladesh. A total of 41 phytoplankton genera belong to Chlorophyceae (15), Bacillariaophyceae (14), Cyanophyceae (8) and Euglenophyceae (4) were recorded whereas Bacillariaophyceae (37.02%) was the most dominant. The highest cell density (22.71×104 cell L–1) was recorded in pre-monsoon. Diversity indices were also significantly higher in pre-monsoon. The species diversity, evenness and richness varied from 2.51–3.79, 0.57–0.90 and 4.65–7.50 respectively. Difference in phytoplankton assemblage with an overall average dissimilarity value of 52.56 % was recorded. Cyclotella (3.60%), Bacillaria (3.13%), Volvox (2.95%), Spirulina (2.92%) and Euglena (2.88%) were the five most contributory species to the seasonal variation. Gross Primary Production, Net Primary Production and Community Respiration values ranged from 0.90–2.49, 0.68–1.60 and 0.35–0.89 mgCm–3day–1 respectively. Alkalinity and Chl-a showed significant positive correlation with GPP, NPP and CR. Pre-monsoon was the most productive phase whereas the monsoon season was the least productive. The current study produced valuable baseline data that will aid in the formulation of wetland conservation and management strategies

The common diseases of freshwater ornamental fishes and the treatments applied by local fish owners in Puerto Princesa City, Palawan, Philippines

The demand for freshwater ornamental fish as anti-stress pets and a source of livelihood had become popular in Puerto Princesa City (PPC), Palawan during the surge of COVID-19. However, the occurrence of many health-related issues become a major problem due to a lack of experience and knowledge of some fish owners engaged in freshwater ornamental fish keeping and breeding methods. This study was conducted on 13 local fish owners to determine the common diseases in freshwater ornamental fishes, affected species and their life stages and the treatments and preventive measures. A total of 19 diseases were recorded infecting the freshwater ornamental fishes in PPC. White-spot or ich disease was the most prominent disease, followed by tail and fin rot. Juvenile and adult of goldfish (Carassius auratus), Siamese fighting fish (Betta splendens) and guppy (Poecilla reticulata) were the most infected fishes, observed by 1 (7.7%) to 5 (38.5%) fish hobbyist. The salt bath was the most common treatment applied. Measures to increase the awareness of local fish hobbyist in terms of fish handling, breeding and health management is highly suggested to continuously improve and expand this developing fishery in Palawan as a source of income and pet companion