Wild Stocks Research Articles

Population Genomic Analyses of Wild and Farmed Striped Catfish Pangasianodon Hypophthalmus in the Lower Mekong River

The striped catfish Pangasianodon hypophthalmus is an important freshwater fish cultured in many countries where the collection of wild brooders is still widely practiced. Global farming development of this species makes use of significant natural resources that pose challenges for the genetic diversity of striped catfish. Hence, this study aims to conduct a systematic genetic diversity assessment of wild and farmed catfish stocks collected from four major pangasius-farming countries, using a new genotyping by sequencing platform known as DArT-seq technology. Our population genomic analyses using 7263 single-nucleotide polymorphisms (SNPs) after high-quality-control showed that there were two distinct populations of striped catfish in the lower Mekong river: (i) wild catfish from Thailand and (ii) catfish from Cambodia and Vietnam. The genetic diversity was greatest (0.363) in the wild stock from Thailand, but it was lower in farmed and wild stocks in other countries (0.049 to 0.088). The wild stocks were more genetically diverse than the farmed animals (0.103 vs. 0.064). The inbreeding coefficient ranged from 0.004 and 0.109, with the lowest value (−0.499) in the wild animals from Thailand. Molecular inference methods revealed high degree of historical effective population size (1043.9–1258.4), but there was considerable decline in the contemporary estimates in all populations (10.8 to 73.6). Our additional analyses calculating divergent times and migration patterns showed that the wild catfish from Thailand stand out as separate lineages, while those from Cambodia and Vietnam are genetically identical. Our results also indicated that the cultured stock in Bangladesh originated from the lower part of the Mekong river. These findings have significant practical implications in the context of genetic selection and conservation of striped catfish in the region. Collectively, they will contribute to the sustainable development of the striped catfish sector in these countries.

Comparative Characteristics of Percentage Edibility, Condition Index, Biochemical Constituents and Lipids Nutritional Quality Indices of Wild and Farmed Scallops (Flexopecten glaber)

The consumption of seafood has considerably increased over recent decades; however, as wild seafood stocks are limited, the cultured ones represent a possible valuable alternative. The purpose of this study was to compare wild and cultured scallops, Flexopecten glaber, on the basis of their marketability indices and biochemical characteristics. Wild and cultured specimens were harvested from the Ionian Sea (the Central Mediterranean Sea). Protein and lipid were significantly different between scallops, with the values of protein of 8.50 and 11.6 g/100 g and lipid of 1.45 and 1.70 g/100 g for wild and cultured scallops, respectively. Regarding fatty acids (FAs), statistical differences were also detected. The cultured species showed significantly (p < 0.05) higher polyunsaturated fatty acids (PUFAs) than its wild counterpart. Eicosapentaenoic (EPA, 20:5 n3) and docosahexaenoic acid (DHA, 22:6:3) were the major polyunsaturated fatty acids, although only DHA showed significant differences between wild and culture scallops (p < 0.05). The ratio of n3/n6 PUFA showed high values, with 2.7 and 3.1 for wild and cultured scallops, respectively. The atherogenic and thrombogenic indices and hypocholesterolemic/hypercholesterolemic fatty acid ratio indicated an import role in human diet. The appreciated nutritional properties of this species could support the interest to promote its cultivation, ensuring high food nutritive value for the purchasers.

An improved micropropagation protocol for the ex situ conservation of Mitragyna parvifolia (Roxb.) Korth. (Rubiaceae): an endangered tree of pharmaceutical importance.

Mitragyna parvifolia (Roxb.) Korth., commonly known as “Kadam,” is an endangered and pharmaceutically valued tree of the family Rubiaceae. The numerous medicinal properties are attributed to the various alkaloids of this plant. Poor seedling survival (due to very small size of seeds, approximately 10,000 per gm), overexploitation and habitat destruction are the major constraints in conserving the wild stocks of this species. This paper reports a significant, improved, and repeatable micropropagation protocol of M. parvifolia using nodal explants of a mature tree. Nodal explants harvested during spring season from the lopped tree differentiated the maximum number of axillary shoots (5.3 ± 0.82 per node) on full-strength Murashige and Skoog (MS) medium containing 3.0 mg L−1 6-benzylaminopurine (BAP) and additives (25 mg L−1 each of adenine sulfate, L-arginine, and citric acid and 50 mg L−1 ascorbic acid). Shoots were amplified in vitro through (1) recurrent transfer of mother explants and (2) subculturing on fresh nutrient medium. The greatest number of shoots (13.4 ± 1.26) with an average length of 6.2 ± 1.03 cm was produced after 4 wk on MS medium containing 0.5 mg L−1 BAP, 0.25 mg L−1 kinetin (Kin), 0.1 mg L−1 Indole-3-acetic acid (IAA), additives, 100 mg L−1 activated charcoal (AC), and 0.8% (w/v) agar. This is the first report of concurrent ex vitro rooting and acclimatization (CEVRA) in M. parvifolia. About 90% micropropagated shoots rooted ex vitro on pulse treatment of 500 mg L−1 Indole-3-butyric acid (IBA; for 5 min) and produced 8.5 ± 0.97 roots per shoot with an average length of 9.40 ± 1.06 cm, after 5 wk. Over 80% of CEVRA plantlets were successfully transplanted to the soil in field. The defined protocol can be employed for conservation ex situ and restoration/rehabilitation/reintroduction in situ of M. parvifolia.Electronic supplementary materialThe online version of this article (10.1007/s11627-020-10089-6) contains supplementary material, which is available to authorized users.

Genetic analysis of body weight in wild populations of medaka fish from different latitudes.

The genetic bases of growth and body weight are of economic and scientific interest, and teleost fish models have proven useful in such investigations. The Oryzias latipes species complex (medaka) is an abundant freshwater fish in Japan and suitable for genetic studies. We compared two wild medaka stocks originating from different latitudes. The Maizuru population from higher latitudes weighed more than the Ginoza population. We investigated the genetic basis of body weight, using quantitative trait locus (QTL) analysis of the F2 offspring of these populations. We detected one statistically significant QTL for body weight on medaka chromosome 4 and identified 12 candidate genes that might be associated with body weight or growth. Nine of these 12 genes had at least one single nucleotide polymorphism that caused amino acid substitutions in protein-coding regions, and we estimated the effects of these substitutions. The present findings might contribute to the marker-assisted selection of economically important aquaculture species.

A newly developed genetic sex marker and its application to understanding chemically induced feminisation in roach (Rutilus rutilus).

Oestrogenic wastewater treatment works (WwTW) effluents discharged into UK rivers have been shown to affect sexual development, including inducing intersex, in wild roach (Rutilus rutilus). This can result in a reduced breeding capability with potential population level impacts. In the absence of a sex probe for roach it has not been possible to confirm whether intersex fish in the wild arise from genetic males or females, or whether sex reversal occurs in the wild, as this condition can be induced experimentally in controlled exposures to WwTW effluents and a steroidal oestrogen. Using restriction site-associated DNA sequencing (RAD-seq), we identified a candidate for a genetic sex marker and validated this marker as a sex probe through PCR analyses of samples from wild roach populations from nonpolluted rivers. We also applied the sex marker to samples from roach exposed experimentally to oestrogen and oestrogenic effluents to confirm suspected phenotypic sex reversal from males to females in some treatments, and also that sex-reversed males are able to breed as females. We then show, unequivocally, that intersex in wild roach populations results from feminisation of males, but find no strong evidence for complete sex reversal in wild roach at river sites contaminated with oestrogens. The discovered marker has utility for studies in roach on chemical effects, wild stock assessments, and reducing the number of fish used where only one sex is required for experimentation. Furthermore, we show that the marker can be applied nondestructively using a fin clip or skin swab, with animal welfare benefits.

Competitive feeding interactions between native Ostrea edulis and non-native Crassostrea gigas with implications of introducing C. gigas into commercial aquaculture in the eastern Adriatic Sea

In order to detect the possible regulatory effect of non-native C. gigas on the native O. edulis, under aquaculture conditions, feeding interactions between them were investigated in a highly productive environment of Lim Bay (Adriatic Sea). The present study uses a multi-methodological approach, including stomach content, DNA barcoding and stable isotope analysis to elucidate the feeding ecology of two oyster species. The research confirmed a high overlap throughout the year in the feeding traits among native and non-native oyster species. Competition for food was not the only relationship that exists between the investigated species as the presence of O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. Findings are not in favour of introducing C. gigas to commercial aquaculture in any new areas in the Adriatic Sea and support the need to improve the existing O. edulis aquaculture and conserve its wild stocks.

Identifying peak breeding season and estimating size at first maturity of mud crab (Scylla olivacea) from a coastal region of Bangladesh

Recently mud crab (Scylla olivacea) has emerged as a potential export commodity. Its farming is increasing rapidly in Bangladesh because of its lucrative price and high demand in international market. However, the farming or fattening of mud crab is totally dependent on capture of wild crablets. A huge quantity of mud crabs is being caught indiscriminately from nature and thus putting intense pressure on its wild stock, which is a major concern of conservation. Imposing ban at peak breeding season and setting a legal capture size are considered effective management tools for safe migration and spawning of berried females. There is contradictory information on breeding season of mud crab in Bangladesh. Thus, it is crucial to identify the peak breeding season of it and to formulate conservation policies to protect the berried crabs. Live crabs were collected year-round from the river adjacent to southwest part of Sundarbans. Although mud crab breeds throughout the year, March–April was identified as the peak breeding season of it. The second peak was observed in August–September. The highest abundance of crablets (1–2 months age) was recorded in May–June, and the lowest in January–February. Immature crablets were found all through the year that proves that mud crab is a continuous breeder. The highest amount of GSI value (11.6) was observed in February–March, which indicates that the breeding is very near. The size at first maturity (M50) was estimated as 95.5 mm CW which lied at size class 91–100 mm (CW). The findings from the study will assist in fixing up the banning time and thus protecting the mother crabs; and will assist in formulating police to conserve and protect juvenile crabs in the sense that the minimum legal capture size of crabs will allow the adults to mate and spawn at least once before their capture.

Ranching in river Ganga: A protocol of practices for indigenous carps germplasm enhancement and conservation in river

River ranching of fish species is one of the managerial techniques to conserve the native germplasm in the open waters. In the recent years most of the rivers worldwide including the river Ganga have been facing serious pressure including water abstraction, water obstruction, pollution and climate change. In this backdrop, river ranching of the identified indigenous carp species through artificial breeding of native brooders of Labeo catla (Catla), Labeo rohita (Rohu), Cirrhinus mrigala (Mrigal) and Labeo calbasu (Calbasu) were carried out in Ganga. The seeds of these species were raised to more than 100mm size before ranching to reduce the chances of natural mortality. More than 30 lakh fingerlings were ranched at different sites of the middle (Pryagraj to Farakka) and lower stretches (Farakka to Howrah) of river Ganga with the objective to enhance the IMC population keeping the native germplasm unpolluted. This study describes a protocol of river ranching of fish seeds through artificial breeding of wild fish stocks, nursery managements and release and may be suitable for other rivers also. Key words River Ganga; Conservation; Ranching; IMC; NMCG

Fish as feed: Using economic allocation to quantify the Fish In : Fish Out ratio of major fed aquaculture species

Efficiency assessments of marine ingredient use in aquaculture are required to fully understand their contribution to global seafood supply and their impacts on all UN Sustainable Development Goals. Fish In: Fish Out (FIFO) ratios have become the principal metric used to ensure aquaculture does not negatively impact wild fish stocks. However, several approaches have been advocated to calculate the FIFO ratio and there have been criticisms that the different approaches employed lead to over- or under- estimates of the dependence of aquaculture on marine ingredients. Critically, FIFO does not align with Life Cycle Assessment as a measure of other environmental impacts. In this paper we present an alternative method to calculate the FIFO ratio based on the principle of economic allocation (economic Fish In: Fish Out – eFIFO) as commonly used in Life Cycle Assessments. Economic allocation acts as a proxy for the nutritional value of ingredients and places higher importance on the more limiting co-products generated and their relative demand. Substitution of marine ingredients by alternate feed ingredients has significantly reduced the amount of fishmeal and fish oil in aquafeed formulations for most farmed fish species, resulting in a continually decreasing FIFO ratio. Results show that most aquaculture species groups assessed in this study are net producers of fish, while salmon and trout aquaculture are net neutral, producing as much fish biomass as is consumed. Overall, global fed-aquaculture currently produces three to four times as much fish as it consumes. Tracking historical prices of fish oil against fishmeal, the relative higher price of fish oil leads to relatively higher allocation of fish to fish oil compared to fishmeal. This leads to relatively higher eFIFO for species with high fish oil requirements.

Seaweed Reproduction and Harvest Rebound in Southcentral Alaska: Implications for Wild Stock Management

In Alaska, interest in harvesting seaweeds for personal use is growing and information on potential impacts of this activity on sustainability of wild populations is lacking. This study provides information on reproductive timing and size, standing crop, and harvest rebound of three commonly harvested seaweeds in Southcentral Alaska: the rockweed, Fucus distichus; the sugar kelp, Saccharina latissima; and the bull kelp, Nereocystis luetkeana. From March through October 2018, seaweeds were surveyed for reproductive status and harvested to determine how much biomass was available. From the harvests, individuals were measured to determine the size when they first become reproductive. Harvested plots were re-harvested to determine biomass regrowth after 2, 4, and 6 months. Fucus and Nereocystis were broadly reproductive over the summer, while Saccharina was not. The presence of reproductive Fucus and Nereocystis throughout the summer could buffer the impacts of late season harvesting. Depending on the species (e.g., Fucus), individuals that became reproductive at a larger size were associated with lower density and lower biomass areas with slower recovery. The amount of biomass available for harvest and the amount that regrew following a harvest were temporally variable but had spatial differences that were consistent throughout the summer. Regrowth following harvesting for all three species was generally low after only 2 months, but the amount of biomass after 6 months post-harvesting was sometimes comparable to non-harvested areas. This study demonstrated that to varying extents, seaweed harvesting may be sustainable if timing of reproduction, available biomass, and regrowth are all considered.

The role of the gut microbiome in sustainable teleost aquaculture.

As the most diverse vertebrate group and a major component of a growing global aquaculture industry, teleosts continue to attract significant scientific attention. The growth in global aquaculture, driven by declines in wild stocks, has provided additional empirical demand, and thus opportunities, to explore teleost diversity. Among key developments is the recent growth in microbiome exploration, facilitated by advances in high-throughput sequencing technologies. Here, we consider studies on teleost gut microbiomes in the context of sustainable aquaculture, which we have discussed in four themes: diet, immunity, artificial selection and closed-loop systems. We demonstrate the influence aquaculture has had on gut microbiome research, while also providing a road map for the main deterministic forces that influence the gut microbiome, with topical applications to aquaculture. Functional significance is considered within an aquaculture context with reference to impacts on nutrition and immunity. Finally, we identify key knowledge gaps, both methodological and conceptual, and propose promising applications of gut microbiome manipulation to aquaculture, and future priorities in microbiome research. These include insect-based feeds, vaccination, mechanism of pro- and prebiotics, artificial selection on the hologenome, in-water bacteriophages in recirculating aquaculture systems (RAS), physiochemical properties of water and dysbiosis as a biomarker.

Models suggest pathogen risks to wild fish can be mitigated by acquired immunity in freshwater aquaculture systems

The interaction of pathogens between wild and farmed aquatic animal populations is a concern that remains unclear and controversial. Ichthyophthirius multifiliis, a ciliated protozoan parasite, is a pathogen of freshwater finfish species with geographic and host range that causes significant economic losses in aquaculture. Flow-through farming systems may facilitate the transfer of such a parasite with free-living stages between farmed and wild stocks. Here, experimental and field study infection data are used to describe the infection dynamics of Ichthyophthirius multifiliis in rainbow trout using a simple macroparasite model by including host resistance. The study considered flow-through farming systems with a single or two age-class compartments and simulated the transfer of the parasite between farmed and wild fish populations. Results suggest that aquaculture can promote the prevalence of the resistance in wild stocks by increasing the parasite population in the wild environment. At the same time, acquired resistance in the farmed fish population may protect the wild fish population from lethal effects of the parasite by reducing the total parasite population. This study offers a promising mathematical basis for understanding the effects of freshwater aquaculture in disease spread in wildlife, developing risk assessment modeling, and exploring new ways of aquaculture management.

KARAKTERISTIK BIOLOGI KUDA LAUT (Hippocampus spp) SEBAGAI PENGETAHUAN DASAR BUDIDAYANYA

Many species of marine organisms live in Indonesian waters have a potential for aquaculture (fishes, crustaceans, mollusc, echinoderm, and algae). They are cultured for food resources, the basis for cosmetic and natural medicine, and also as ornamental fish for marine aquarium. Seahorse (Syngnathidae: Hippocampus) is a marine fish which has high ecological and economic value. Fishing pressure of wild seahorse increased significantly when buyers offering an attractive price for the catch. High levels of fishing effort keep the wild stocks of seahorses well below the level that could be supported by natural growth and recruitment. Aquaculture for seahorses is very important to support sustainable production and to maintain the wild population in steady condition. Culture technique for seahorses has been developed in some countries, including Indonesia. However, seahorse aquaculture in Indonesia has not been achieved as expected due to the limited understanding of some biological characteristics. This manuscript deliberates some biological characteristics that useful as basic knowledge for seahorse aquaculture.

Marine Aquaculture Impacts on Marine Biota in Oligotrophic Environments of the Mediterranean Sea – A Review

The potential impacts of marine aquaculture are reviewed, focussing both on small-scale local effects near the farm environment and a broad spatial scale of many kilometres that impacts a number of different ecosystem components. Local changes in productivity, biodiversity and behavioural changes of wild fauna affected by nearby farm habitats were examined. Global aquaculture trends of growth perspectives as related to seafood supply, impacts on wild stock and biodiversity depletion, genetic changes in wild fish populations due to the escapement of cultured fish, capture-based aquaculture and its potential impacts on marine habitats were discussed. Adopting integrated principles in planning aquaculture development and respecting the assimilative capacity of a potential farming zone may reduce negative consequences of the aquaculture industry on the marine ecosystem.

Universal reliance on LAL/TAL in bacterial endotoxin detection in drugs and parenteral - An ecological and economic perspective


 Introduction: Endotoxin detection and quantification in biological drugs and parenteral is a crucial step in helping us to be confident in process control (IPC) and product release decisions. Food and Drug Administration (FDA) approves either Limulus Amebocyte Lysate (LAL) /Tachypleus Amebocyte Lysate (TAL) derived from blue blood of horseshoe crabs to detect and quantify endotoxin. This in turn increases harvest pressure on wild crabs for biomedical bleeding practice which eventually leads to post bleeding mortality up to 30%. In economic perspective, the LAL/TAL industry worth more than 50 million USD annually. Methods: Numbers of methods were adopted to enhance the accuracy of endotoxin detection, including gel clot, turbidimetric and chromogenic method. Results: However, all these methods require crabs either from wild or from captive for bleeding purpose. Though, various conservative measures are being taken, the habitat degradation and anthropogenic pressures on wild crab population is still beyond control and leads to unsustainable utilization of natural stock. Conclusions: Due to an increased demand of LAL/TAL, the present review paper addresses the issues related to Eco-economical viewpoint on sustainable utilization of wild stock for future LAL/TAL industry. It also addresses pros and cons of recent advanced sensor technology in rapid and low cost detection of endotoxin.

The Impacts of Sublethal Nitrite Exposure on Goldfish (Carassius auratus) Microbiomes

Around 50% of fish consumption comes from aquaculture. An increase in world population and food demands requires fish production to dramatically increase over the next decade. One of the major obstacles of increasing aquaculture production is disease. Thus, a key aspect of aquaculture research is understanding immune health and the spread of disease within farmed populations and into wild stocks. A major portal for pathogen entry in fish is the nose; nasal infections tend to be severe and result in damage to the olfactory and nervous systems. Immune health is impacted by numerous systems including the microbiome. The microbiome trains the immune system, provides a barrier for pathogens, and helps maintain homeostasis. Therefore, dysbiosis, a disruption of the microbiome due to changes in diet, exposure to pollutants, antibiotic consumption, and physiological stress, can contribute to disease. One common pollutant in water is agricultural runoff containing nitrates and nitrites, which are known to cause stress in fish and can be deadly in some concentrations. However, it is unknown how nitrites impact the microbiomes of sensitive tissues and how these changes impact immune health. I hypothesize that increased nitrite concentrations will cause dysbiosis of the microbiome resulting in changing abundance and diversity of the microbiome. This work aims to determine the impacts of sublethal levels of nitrite on the nasal microbiome and compare it to the microbiomes of the gills and gut. For 2 months goldfish (10 fish/30L tank) were held under various nitrite concentrations, 0.0mM (control), 0.01mM, 0.1mM, and 1.0mM. The system utilized continuous aerated water flow at 24°C to maintain the desired concentrations of nitrite. Tissue samples were collected from each fish with water collected to serve as a control to determine the host‐specific microbiome. The DNA from the tissues were extracted, amplified, and prepared as a library for sequencing using 16S rRNA gene primers for Illumina MiSeq. The sequences were analyzed using the DADA2 pipeline in R and MaAsLin from Galaxy. The gill microbiome showed no significant changes in abundance compared to the control treatment. The nose microbiome appears to show an increase in diversity compared to the control microbiome; however, these changes were not determined to be significant. Both the gut and water microbiomes showed significant changes in abundance compared to their control levels, with the gut microbiome changing the most. Sublethal levels of nitrite exposure significantly increase the diversity of the microbial communities of the water and the gut microbiomes. There are also some indications that the nose and gill microbiomes are impacted, however, small sample sizes could be obscuring the changes. These impacts imply that sublethal nitrite concentrations can cause dysbiosis of the fish microbiomes and could have negative impacts of fish health.

Efficacy of restocking an estuarine-resident species demonstrated by long-term monitoring of cultured fish with alizarin complexone-stained otoliths. A case study

Long-term monitoring data and models have been used to explore the efficacy of restocking an estuarine-resident teleost species. Juveniles of Acanthopagrus butcheri were cultured from broodstock from the Blackwood River Estuary in 2002 and their otoliths stained with alizarin complexone. 150,000 marked juveniles were released into the Blackwood River Estuary at three months old in early 2003, with the stain in their otoliths subsequently remaining visible during the following 16 years. Samples of A. butcheri were obtained annually from a commercial gill net fisher and at intervals by fishery-independent methods. Commercial catch per unit effort was positively related to freshwater discharge. Indices of year class strength, derived from annual age-frequency distributions and assuming length-dependent natural mortality, demonstrate that between 1993 and 2012, natural recruitment to the population was only strong in 1999 and 2008 and was not significantly related to freshwater flow. The number of wild stock A. butcheri ≥ minimum legal length (250 mm total length), comprising mainly the 1999 year class, were estimated to have declined sequentially to only ∼12,000 fish in 2010. The restocked fish contributed between 61 and 73 % to the total number of fish in the commercial catches between 2007 and 2010 and their numbers remained at > 10 % of their number at release until 2011. The contribution of the 2008 year class, of which ∼50 % had been estimated as derived from restocked fish, increased from 20 % of the commercial catch in 2012 to between 50 and 80 % between 2013 and 2018. A progressive decline in growth of year-class groups of wild stock fish, from 1970-1998 to 2008-2011, is considered to reflect the detrimental effects of hypoxia. Restocked fish grew less rapidly than younger and older year-class groups of wild stock fish, suggesting that the growth of cultured fish may have been compromised by hatchery processes. The large contributions made by restocked fish to commercial catches over several years and to future generations highlight the efficacy of restocking for replenishing and sustaining a depleted population of an estuarine-resident species.

Genetic Assessment of a Black Rockfish, Sebastes schlegelii, Stock Enhancement Program in Lidao Bay, China Based on Mitochondrial and Nuclear DNA Analysis

The black rockfish Sebastes schlegelii is a commercially important fish species for marine fishery stock enhancement in Asia. This work aimed to evaluate the potential genetic impacts of releasing hatchery-reared juvenile black rockfish on wild stock in Lidao Bay, China. A partial sequence of the mitochondrial DNA (mtDNA) control region and 38 microsatellite DNA loci were used to assess the genetic impact. The haplotype diversity parameter (h) and nucleotide diversity parameter (π) in hatchery-released stock were 0.902 and 0.00483, respectively. The h values in wild stock before stock enhancement and the mixed stock after enhancement were 0.970 and 0.939, respectively, and the π values were 0.00581 and 0.00526, respectively. The mean effective numbers of alleles (Ne) in hatchery-released stock was 4.76, the mean polymorphism information content (PIC) was 0.674, the observed heterozygosity (Ho) was 0.668, and the expected heterozygosity (He) was 0.697. In wild stocks before stock enhancement and the mixed stock after enhancement, the Ne, PIC, Ho, and He values were 6.01 and 5.82, 0.698 and 0.716, 0.709 and 0.741, and 0.735 and 0.754, respectively. These results showed that there was no marked decrease in the hatchery-released stock, although it displayed slightly lower levels of genetic diversity and heterozygosity than the wild stock. The mixed stocks after S. schlegelii release exhibited similar genetic diversity to that of the wild stock before release, and the genetic variation in the natural stock did not decrease after stock enhancement. Moreover, both the fixation index (FST) and AMOVA analysis clearly showed minimal population structure differences between the hatchery-released and wild stocks, and the wild stock before enhancement and the mixed stock after enhancement. These results showed that stock enhancement may not cause any negative genetic effects on wild S. schlegelii stock in Lidao Bay over the short term. Accordingly, we propose that the current breeding and release methods are appropriate for conserving the genetic diversity of S. schlegelii. However, our results also showed a slight reduction in some genetic parameters, such as allelic diversity, heterozygosity, and effective population size, in the mixed stock after restoration. Consequently, long-term genetic evaluation might be required.

Stock enhancement of abalone, Haliotis asinina, in multi-use buffer zone of Sagay Marine Reserve in the Philippines

Donkey's ear abalone (Haliotis asinina) is a gourmet seafood export of the Philippines but its wild stock is at risk due to high fishing pressure. This paper aims to show evidences that abalone seeds produced in hatcheries can be used to rehabilitate its fisheries in multi-use buffer zones of marine reserves. This study released hatchery-reared abalone juveniles in a community-based resource enhancement site located in multi-use reef surrounding Molocaboc. This island is populated by fisherfolks who participated in protecting the 4000 m2 coralline release site. Molocaboc Reef comprise the buffer zone of Sagay Marine Reserve in Negros Occidental province in central Philippines. Data obtained during monthly monitoring of the release site from 2011 to 2016 showed that hatchery-reared abalone established together with its wild counterparts. Baseline wild abalone catch per unit effort (CPUE = 3 divers 1 h fishing) is 0.005/100 m2 in 2011. Mean monthly CPUE after release increased to 53 hatchery-reared and wild individuals combined. The mean shell length, body weight and body mass index of the hatchery-reared individuals (6.4 cm, 70.9 g, 10.5 g/cm) is not significantly different from those of the recovered wild stocks (6.9 cm, 85.0 g, 12.0 g/cm). The stocks recovered in the midst of undisrupted fishing activities in areas immediately outside and beyond the release site. Thus, mass production of seeds of overfished species is advised to repopulate degraded fisheries, improve catch of fisherfolks living within buffer areas of marine reserves and contribute to production and trade of high-value species.

Mud crab fishery in climate vulnerable coastal Bangladesh: an analysis towards sustainable development

Developing countries are far more vulnerable to climate change impacts than industrialised countries. Most of the world’s poor live in South Asia where they have limited livelihood options that have become even narrower in recent years, indicating a need for alternative income-generating options. Mud crabs (Scylla spp.) are considered to have promising prospects in different parts of the world including Bangladesh, a well-known region for its vulnerability to climate change. At present, this fishery has become a growing venture in coastal Bangladesh, primarily due to the potential of the export market and availability of seed locally. This study included a calculation of the Human Development Index linked to mud crab fishery (HDIMCF) and a strengths, weaknesses, opportunities and threats (SWOT) analysis to clarify the present status of and strategic directions for the mud crab fishery, for the first time. Results revealed an intermediate level of development of mud crab aquaculture, indicating potential alternative livelihood opportunities for vulnerable coastal communities. The SWOT analysis revealed that positive factors, both internal (strengths) and external (opportunities), predominate over negative factors (weaknesses and threats) and that the fishery can be an alternative livelihood option for vulnerable coastal communities. Despite noticeable diversification of the mud crab fishery, dependence on wild seedstock and possible over-exploitation in the wild appear to constrain sustainable development of the fishery. This study’s findings suggest undertaking immediate wild crab stock assessment for determining current status of wild populations. Moreover, modification of the Government of Bangladesh’s existing mud crab policy is needed to better meet growing demand and sustainability of the fishery. Recommendations of this study may be of help in guiding responsible integrated coastal fisheries management and policy.