Adoption of Vietnamese Good Agricultural Practices (VietGAP) in Aquaculture: Evidence From Small-Scale Shrimp Farming

The increasing demand by international customers for high-quality shrimp products has led to the introduction of various certificates of traceability intended to validate quality products in Vietnam. The Vietnamese good agricultural practices (VietGAP), better known in aquaculture as the Vietnamese good aquaculture practices, has emerged as a reliable certificate for small-scale farmers and a prerequisite for international certification. This study investigates factors affecting applications for VietGAP by small-scale shrimp farmers in Vietnam. Cost-benefit analysis and binary logistic regression approaches were used to categorise shrimp farms with and without VietGAP certification. Findings indicated that while the adoption of VietGAP raised production costs by 14.5 %, it could increase net profit by up to 22 %. The increase in net profit is from increased productivity and antibiotics and chemical-free products in shrimp farming, helped fetch better prices. The results also revealed three factors that positively influenced the farmers’ decision to acquire VietGAP; education, farm size, and production system. Shrimp farmers with longer schooling years, larger farms, and those who possess cooperative/farming cluster membership are more likely to acquire VietGAP certification. The results imply that the VietGAP certification should be better promoted to cooperative production forms of farming, by strengthening the schooling year of farmers and increasing awareness of VietGAP certification to farmers who operate shrimp farms of 5,000–9,000 m2.

Intensive Fishing Effort and Market Controls as Management Tools for Invasive Aquatic Species: A Review

Invasive aquatic species may disrupt ecosystems and cause socioeconomic damage. Biosecurity protocols were developed to prevent transport and unintended introductions of invasive species, but less attention has been paid to management once they become established. The use of classical fisheries stock assessment to determine levels at which selectively targeted fisheries elicit recruitment overfishing is discussed. Case studies of several species of invasive aquatic organisms, including lionfish Pterois spp. two species of mytilids and three species of crayfish, including Faxonius rusticus (Girard, 1852), are discussed as examples. Fecundity as measured by egg production rate (EPR) is a key factor determining how the various species react to fishing pressure. Ecosystem modelling of predatorprey relations between indigenous and invasive aquatic species suggests that restricting fishing effort on indigenous predators of invasive prey may be as effective in managing invasive species in lieu of directly increasing fishing effort on the targeted species itself. Invasive mytilids Dreissena polymorpha (Pallas, 1771) and Mytella strigata (Hanley, 1843) may not be effectively controlled by intensive fishing effort due to high EPR values. However, crayfish that brood offspring and exhibit much lower EPR values may be ideal candidates for stock assessment and setting fishing effort targets to promote recruitment overfishing. Recommendations for managing invasive aquatic species include: collecting data on population dynamics of the invasive species; assessing predator populations; developing fisheries that target the invasive species; and collecting socioeconomic data to understand the human dimensions of the impacts of the invasive species and inform subsequent policy development.

Trade Potential of Indigenous Ornamental Fishes of Arunachal Pradesh, India

Arunachal Pradesh is rich with networks of drainage systems with enormous wild fish diversity due to varied climatic and topographical features. Most of the streams harbour very alluring small indigenous minnows, loaches, catfishes and barbs that have hardly been exploited for the ornamental fish market. If these aquatic resources are sustainably utilised as a trade commodity, then the pattern of livelihood of the local populace may be uplifted economically. The present investigation was undertaken to establish the market potential of certain indigenous ornamental fishes of Arunachal Pradesh. The survey was conducted during 2019–2020 for 6 months (October–March) based on the feasibility of accessible collections. A total of 52 ornamental fish species under 6 orders and 15 families were documented and collected during the surveys in various streams and rivers. The collection showed that 4 species namely Balitora brucei Gray, 1830, Aborichthys kempi Chaudhuri, 1913, Schistura devdevi Hora, 1935, and Neolissochilus hexagonolepis (McClelland, 1839) were recorded under near threatened; Lepidocephalichthys arunachalensis (Datta & Barman, 1984) and Botia rostrata Günther, 1868, under endangered and vulnerable categories, respectively as per International Union for Conservation of Nature (IUCN) status. The species documented exhibiting natural ornamental features herein considered an indigenous ornamental fish (IOF) for depicting their market demand showing the minimal price of each individual species towards the development of organised trade in Arunachal Pradesh.

Effects of Mixing Duration and Raw Materials on the Physicochemical, Microstructural and Sensorial Properties of Sausages Prepared From Red Tilapia (Oreochromis sp.)

Tilapia can be commercialised to produce sausages. However, the use of minced tilapia or tilapia surimi as the raw material and different mixing durations of the ingredients using the bowl cutter during the sausage production could affect the quality of the products. This study determined the effects of different mixing durations (10, 15 or 20 min) on the physicochemical, microstructural and sensorial properties of sausages made from minced tilapia and tilapia surimi. The washing of the minced tilapia during the surimi production significantly increased the tilapia surimi moisture content and pH, while reducing the protein, fat and ash contents. Subsequently, the addition of other ingredients to produce the sausages influenced the moisture, fat, ash and carbohydrate contents of both types of sausages. The type of raw material and mixing duration showed significant interactions in terms of linear expansion, water holding capacity and colour properties of the sausages. Individually, the tilapia surimi sausage had a better linear expansion, cohesiveness, colour and sensory acceptability than the minced tilapia sausage. The mixing times of 15 and 20 min produced better results for the physicochemical and sensory properties of both types of sausages. However, the gel strengths of both types of sausages were better when mixed for 15 min and the microstructure images supported this. Based on the results obtained, this study concluded that tilapia surimi as the raw material with 15 min of mixing duration is recommended to produce a better-quality sausage.

Effectiveness of Adaptive Real-Time Closures for Managing Migratory Species in Data-Limited Multispecies Fisheries

Fixed closure (FC) is a standard fisheries management tool for protecting sensitive species or species requiring conservation. However, an FC might not effectively manage migratory species because of the large uncertainties of their migration. Adaptive real-time closure (ARTC) is a tool that updates closure areas according to the latest information. This study aimed to evaluate the effectiveness of ARTC to conserve sensitive species for data-limited fisheries by a series of simulations using migration models with hotspots. In the single species simulation, the conservation ratio for the sensitive species in FC varies widely at greater migration uncertainty. In ARTC, a longer duration of a hotspot resulted in a higher conservation ratio. When the mean duration of hotspots was medium or long, the conservation ratio for the sensitive species was more than 50 % in more than 99 % of the simulation trials. In multispecies fisheries, a clear trade-off was observed between the conservation ratio of sensitive species and other species. ARTC was more effective than whole closure when the proportion of sensitive species was high or without closure when the proportion was low. Conditions in which ARTC was most appropriate were described for hotspot duration, increased numbers of individuals in a hotspot, and the relative value of conservation, representing the ratio of the value of conserving sensitive species to one of catching other species.

Bioeconomic Approach for Assessing Status of Trawl Fishery in the Straits of Malacca

The Straits of Malacca provides half of Malaysia’s total marine fish and seafood supply. Due to depleted fish stock, the Malaysian Government has established a comprehensive legal framework to reduce overfishing in the Straits over the last five decades. However, there are limited scientific studies on the current status of stock recovery. This paper aims to use bioeconomic approach to determine the current trawl fishery status in the Straits. Various statistical tests showed that the Clarke-Yoshimoto-Pooley model was better than the Schnute model in predicting and thus used to estimate the crucial bioeconomic parameters. The current yield and standardised effort of 239,692 tonnes and 931,692 standard fishing days were very close to the estimated biological maximum sustainable yield (239,915 tonnes) and above 18 % of the standardised effort (763,649 standard fishing days) to achieve it. The maximum economic yield was estimated at 201,542 tonnes while the corresponding standardised effort was 396,799 standard fishing days indicating serious economic overfishing in the Straits. If the current effort can be reduced by 57 %, fish biomass and economic rent will increase by 97 % and 835 %, respectively. A price sensitivity analysis predicted that demand-pull fish price inflation could exacerbate the overfishing problem, particularly under unrestrained environment. A 50 % increase in price could lead to a 132 % increase in fishing effort from the base case. The findings of this paper provide valuable insights for fishery managers to refine their existing fishery management program to achieve sustainable fishery for the future.

Deep-Water Japanese Blunthorn Lobster Palinustus waguensis Kubo, 1963: First Estimates of Life History Parameters From the Southwest Coast of India

Palinustus waguensis Kubo, 1963, is the deep-sea Japanese blunthorn lobster belonging to the Family Palinuridae. It is a species that has been rarely reported, living in rocky habitats on deep-reef slopes at a depth of 100–250 m. An estimated catch of 100 kg of P. waguensis consisting of 113 males, 54 females, and 23 berried lobsters were collected during the first fortnight of January 2019 from the multi-day shrimp trawls operating off Sakthikulangara, Kerala, India. The mean total length was recorded as 112.3 mm in males, 102.6 mm in females. The parameters of the length-weight relationship were estimated as, a = 0.041, b = 2.84 for males and a = 0.05, b = 2.86 for females, which were not significantly different (P > 0.05, r2 > 0.90) between the males and females. The relative condition factor (K) in the males and females of P. waguensis ranged from 2.07–4.96 and 1.87–3.86, respectively, attributing to the better feeding efficiency in males. Food and feeding analysis revealed the dietary content as fish (53 %), crab (23.5 %), shrimp (7.8 %), digested matter (11.6 %), and foraminifera (4 %). Feeding intensity analysis about the fullness of the stomach showed the specimens bearing full stomachs (11.3 %), three-fourth full (9.9 %). Length at 50 % maturity (Lm50) was 96.9 mm. Gonado-somatic index (GSI) ranged from 3.39 to 8.13. The present study forms the first report on the biology of the deep-water Japanese blunthorn lobster, P. waguensis from India.

Periphyton Technology Enhances Growth Performance and Delays Prolific Breeding of Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758), Juveniles

This study evaluated the effect of periphyton technology (PPT) on the growth performance and breeding schedule of Oreochromis niloticus (Linnaeus, 1758) juveniles. Six ponds, each measuring 81 m2 were used for the study. The ponds were applied with agricultural lime at a rate of 4 g.m-2, and fertilised using chicken manure to facilitate primary productivity. The PPT ponds were fitted with two-metre-long eucalyptus poles of 5 cm diameter placed at 50 cm intervals with the regular addition of molasses as a carbon source. Tilapia juveniles were stocked at a density of 3 fish.m-2 in all ponds and fed on a commercial diet of 20 % crude protein (CP) twice daily at 3 % body weight. Fish were sampled weekly for growth and survival data and bi-weekly for fecundity estimates. The PPT-ponds registered significantly higher survival rate (97.50 ± 0.35 %), mean weight (150.69 ± 0.99 g), specific growth rate (SGR) (2.75 ± 0.01), and feed conversion ratio (FCR) (1.29 ± 0.01), than the control ponds, which registered survival (91.15 ± 0.88 %), mean weight (99.23 ± 0.96 g), SGR (2.29 ± 0.00), and FCR (1.58 ± 0.01). There was significantly higher fecundity in the PPT-ponds (2.28 ± 0.09 g.fish-1) than control (1.74 ± 0.06 g.fish-1), with prolific spawning starting 4 weeks earlier in the control ponds than in the PPT-ponds. This study demonstrated the potential of PPT for enhancing tilapia growth while delaying prolific breeding behaviour. Further studies should explore PPT in replacing synthetic hormones for sex-reversal of tilapia fry in hatcheries.

Record of Copepod Parasite (Pennellidae) in Buccal Cavity and Gill Arch of Cultured Groupers, Epinephelus spp. in Batam, Indonesia

The crustacean parasites are the most frequently encountered and cause significant economic loss in mariculture. These parasites infect fish fin, skin, gills, and buccal cavity. This study aims to describe copepod parasite in the buccal cavity of cultured groupers, Epinephelus spp., from Batam waters using morphological and molecular biology approaches. The tiger grouper, Epinephelus fuscoguttatus (Forsskal, 1775), and hybrid grouper, Epinephelus sp. showing lethargy and skin darkening were collected from sea cages. The parasite’s morphology was observed using light and scanning electron microscopes. The genomic DNA was isolated from the parasites and used as a template for amplification of cytochrome oxidase subunit-1 (Cox1) gene and followed by sequencing. The fish exhibited red nodules in the mouth cavity, on the lips, and gill arch in varying numbers and size of nodules. The copepodid, chalimus, and adult copepod stages were found from the nodule. Based on the presence of the oral cone, this parasite belonged to Siphonostomatoida order of copepods. Based on the structure of the caudal ramus with four long and four short setae, the first and second pair legs as biramous, and the third pair leg as uniramous, this parasite belonged to Pennellidae family of copepods. Basic local alignment search tool analysis of this Cox1 showed low homology within 80%, indicating that the DNA sequences of the parasite species were not reported in the GenBank. The unweighted pair group method using arithmetic average phylogenetic trees supported that this parasite belonged to the family Pennellidae. This is the first report on the pennellid parasite infection in the buccal cavity and gill arch of cultured groupers in Batam, Indonesia.

Current Status of Rainbow Trout, Oncorhynchus mykiss (Walbaum, 1792), Fisheries in Munnar Hills of South India

Rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), is a popular cold-water fish species widely distributed and farmed across the globe. In India, rainbow trout fisheries are common in the Himalayan states and the Western Ghats of South India. The introduction of brown trout, Salmo trutta fario (Linnaeus, 1758), in Munnar, Kerala, India, dates back to 1909. As the farming of brown trout was not successful, rainbow trout were introduced in 1932. However, no data regarding trout fisheries post-1970 are available. Hence, this study aimed to assess the current scenario of O. mykiss fisheries by analysing the existing angling and production records and interviewing the officials in charge. The results showed that O. mykiss fisheries in Munnar are currently endangered, and only a few numbers of O. mykiss stock are found in Rajamallay Stream, which is the present stocking site. Studies have shown that destructive fishing, pollution, siltation, and animal intrusion contributed to the decline of trout stocks in this region. Proper conservative measures, good hatchery conditions, adequate broodstock management, feed improvement, and regular seed stocking can improve the production of O. mykiss in Munnar.