Fisheries Enhancement Research Articles

Study on the influence degree of marine ranching on the high-quality development of coastal cities

As an innovative approach to fisheries, marine ranching is subtly transforming the development patterns of coastal cities through the enhancement of fisheries, the professional transition of fishermen, and the restoration of the marine environment. Utilizing the entropy method and the staggered difference-in-differences (DID) method, this paper calculated the high-quality development index (HQDI) of 53 coastal cities from 2010 to 2021 and assessed the influence degree of marine ranching on coastal cities' HQDI. The key findings were as follows. Firstly, marine ranching generally improved the HQDI of coastal cities. Coastal cities with national marine ranching demonstration zones achieved an average increase of approximately 0.83 % in their HQDI compared to those without. Secondly, through the effect of carbon emission reduction, marine ranching contributed to an average increase of approximately 0.84 % in the HQDI. However, the green technology innovation and industrial structure upgrading effects have yet to materialize. Thirdly, this impact varied among coastal cities. When the number of marine ranching exceeded three, the average increase of HQDI was approximately 1.82 %. This effect was pronounced in higher-tier cities, with first-tier cities experiencing an average increase of 1.26 %, second-tier cities an average increase of 1.19 %, and third-tier cities an average increase of 2.18 %. Furthermore, this effect was significant in northern coastal cities, where the average increase was approximately 0.98 %. In coastal cities with low levels of manpower and material resources, this effect was also pronounced, with the HQDI increasing by an average of about 1.01 % and 0.98 %, respectively. Lastly, the spatial econometric analysis revealed a positive spatial spillover effect. This paper evaluated the effectiveness of China's recent marine ranching construction, providing a theoretical and empirical foundation for authorities to formulate targeted policies and measures.

Salmon hatchery strays can demographically boost wild populations at the cost of diversity: quantitative genetic modelling of Alaska pink salmon.

Hatcheries are vital to many salmon fisheries, with inherent risks and rewards. While hatcheries can increase the returns of adult fish, the demographic and evolutionary consequences for natural populations interacting with hatchery fish on spawning grounds remain unclear. This study examined the impacts of stray hatchery-origin pink salmon on natural population productivity and resilience. We explored temporal assortative mating dynamics using a quantitative genetic model that assumed the only difference between hatchery- and natural-origin adults was their return timing to natural spawning grounds. This model was parameterized with empirical data from an intensive multi-generational study of hatchery-wild interactions in the world's largest pink salmon fisheries enhancement program located in Prince William Sound, Alaska. Across scenarios of increasing hatchery fish presence on spawning grounds, our findings underscore a trade-off between demographic enhancement and preservation of natural population diversity. While enhancement bolstered natural population sizes towards local carrying capacities, hatchery introgression reduced variation in adult return timing by up to 20%. Results indicated that hatchery-origin alleles can rapidly assimilate into natural populations, despite the reduced fitness of hatchery fish attributable to phenotypic mismatches. These findings elucidate the potential for long-term demographic and evolutionary consequences arising from specific hatchery-wild interactions, emphasizing the need for management strategies that balance demographic enhancement with the conservation of natural diversity.

Genome-wide association analysis of the resistance to infectious hematopoietic necrosis virus in two rainbow trout aquaculture lines confirms oligogenic architecture with several moderate effect quantitative trait loci

Infectious hematopoietic necrosis (IHN) is a disease of salmonid fish that is caused by the IHN virus (IHNV), which can cause substantial mortality and economic losses in rainbow trout aquaculture and fisheries enhancement hatchery programs. In a previous study on a commercial rainbow trout breeding line that has undergone selection, we found that genetic resistance to IHNV is controlled by the oligogenic inheritance of several moderate and many small effect quantitative trait loci (QTL). Here we used genome wide association analyses in two different commercial aquaculture lines that were naïve to previous exposure to IHNV to determine whether QTL were shared across lines, and to investigate whether there were major effect loci that were still segregating in the naïve lines. A total of 1,859 and 1,768 offspring from two commercial aquaculture strains were phenotyped for resistance to IHNV and genotyped with the rainbow trout Axiom 57K SNP array. Moderate heritability values (0.15–0.25) were estimated. Two statistical methods were used for genome wide association analyses in the two populations. No major QTL were detected despite the naïve status of the two lines. Further, our analyses confirmed an oligogenic architecture for genetic resistance to IHNV in rainbow trout. Overall, 17 QTL with notable effect (≥1.9% of the additive genetic variance) were detected in at least one of the two rainbow trout lines with at least one of the two statistical methods. Five of those QTL were mapped to overlapping or adjacent chromosomal regions in both lines, suggesting that some loci may be shared across commercial lines. Although some of the loci detected in this GWAS merit further investigation to better understand the biological basis of IHNV disease resistance across populations, the overall genetic architecture of IHNV resistance in the two rainbow trout lines suggests that genomic selection may be a more effective strategy for genetic improvement in this trait.

Stakeholders' perception and willingness-to-pay for an aquaculture-based fisheries enhancement program for coastal cod in Southern Norway

The coastal cod fishery in Southern Norway has experienced a significant decline over the last decades. Recreational fishing for cod in the eastern part of the country is currently banned. Fisheries managers have adopted a variety of strategies to sustain the populations for resource users. Aquaculture-based fisheries enhancement has been considered as an alternative intervention to rebuild overexploited cod stock or to improve the opportunity for marine fishing. However, there has been a debate regarding its ecological and social effectiveness among stakeholders. In this paper, we conducted an online contingent valuation survey aiming to understand stakeholders' perceptions and attitude towards restocking of hatchery-produced juveniles as a potential restoration approach to rebuild depleted coastal cod populations and their willingness to pay for the implementation of such an enhancement program in southern Norway. Results indicate that the public has a positive perception to the potential restocking program. The average Willingness-To-Pay (WTP), e.g. fishing license fee, is approximately 175 NOK and 693 NOK if all of the respondents, and only counting those who are willing to, contribute. The introduction of a minimum fishing license fee of 175 NOK (approximately 17€) would cover the cost of production of over 20 million juvenile cod of appropriate size for release. Age of the respondents, the frequency of their fishing trips, and their perception of the decline of coastal cod were the main drivers for the WTP contribution while the amount of the WTP was strongly correlated to targeting particular species, educational level, and place of residence. Considering the critical situation of the coastal cod populations in southern Norway, together with the significant advances in cod rearing techniques, in fish tagging technology and the maturation of fisheries enhancement as science, and the positive stakeholders' perceptions and attitudes towards such an aquaculture-based enhancement program revealed from this study, it may be the time to re-evaluate the potential integration of a holistic cod restocking program within Norwegian coastal zone management.

Catalyzing Conservation: An Analysis of Fish Stock Dynamics in a Marine Protected Area before and after Artificial Reef Deployment

The marine ecosystem’s balance is crucial for sustaining biodiversity and supporting fisheries. Marine protected areas have been increasingly used to enhance marine habitats, yet their impact on fish populations remains a topic of debate. This study focuses on a marine protected area in Kitros, Pieria, in Greece, where an artificial reef was constructed, to understand its influence on coastal fish populations. The objectives were to investigate the changes in fish biomass and abundance, comparing the data from periods before and after the construction of an artificial reef. This research compares the data between 2007 and 2008 with the data between 2016 and 2017, collected with bottom trawl surveys strategically executed prior to and after the artificial reef’s installation. Fish species captured were identified, with their lengths and masses measured. The findings indicate an increase in the biomass and abundance of certain fish species after artificial reef deployment, notably the commercially significant Mullus barbatus and Pagellus erythrinus. The artificial reef in Kitros, Pieria, with its surrounding marine protected area appears to have had a positive impact on the local fish populations over the years, suggesting that it can contribute to marine conservation and fishery enhancement. These results underscore the potential of artificial reefs as tools for marine ecosystem management, offering insights for policymakers and environmentalists into coastal resource management.

Ecosystem-based fishery enhancement through pen culture of Indian major carp Labeo catla in a tropical floodplain wetland of North Eastern Region, India, during COVID pandemic.

The present study was conducted with the objective of developing ecologically and economically feasible pen culture protocols for Labeo catla as an alternate income source for wetland fishers in the context of the COVID-19 pandemic. Yearlings of L. catla (12.33 ± 1.99 cm mean total length and 26.05 ± 6.57 g mean weight) were reared in HDPE pens (500 m2 area each) at three different stocking densities of 3 (SD3), 6 (SD6) and 9 (SD9) no. m-2 in triplicates. Fishes were fed with floating pelleted feed containing 28% crude protein and 5% crude lipid two times daily at 1.5-3% of body weight. During the culture period, fish grew from 26.05 ± 6.57 to 434.61 ± 30.63 g, 306.13 ± 10.68 g and 221.13 ± 14.92 g, respectively, at stocking densities of 3, 6 and 9 no. m-2 respectively. Weight gain percentage and specific growth rate declined with increase in stocking density. Gross fish yield increased with increase in stocking density and was highest at SD9 (657.92 ± 53.55 kg pen-1), while net fish yield increased initially from SD3 to SD6 (594.31 ± 29.72 kg pen-1) and then declined with further increase in stocking density. Important water quality parameters influencing fish growth were measured, and significant difference (p > 0.05) was not observed between treatments (inside pens) and reference site (outside pen at 10-m distance). Weight gain was positively correlated (p < 0.05) to water temperature (r = 0.989) and total phosphorus (r = 0.81). Benefit cost ratio and net return was highest at SD3 (1.61; US $518.88, respectively). Stocking density of 3 no. m-2 can be considered economically feasible for table fish production of L. catla in pens. Post pen culture, monthly income of fishers increased by 10.76-179.11%, with a mean increase of 90.57%, compared to the period of first COVID-19 wave in India. The present findings can provide an impetus for effective utilization of pen enclosures for income generation and livelihood enhancement of small-scale wetland fishers during pandemic.

Revitalizing the Population of Tachypleus tridentatus: A Comprehensive Study Tachypleus tridentatus Conservation in China

Tachypleus tridentatus is an ancient marine arthropod. Currently, the population of Tachypleus tridentatus has decreased rapidly, in 2019, the IUCN Red List officially updated the endangered status of Tachypleus tridentatus to Endangered (EN), indicating a global decline in the resources of this species. However, the lack of data, such as population baseline data, acts as a barrier for this nearshore habitat and medically important species. The results of this paper suggest that the main causes of the decline in the population of the Tachypleus tridentatus darter are overfishing and habitat destruction. In addition, the discussion focuses on three techniques presently employed in China to revive the population of Tachypleus tridentatus, including fisheries enhancement, habitat designation for conservation, and educational programs. The study also examines the advantages and disadvantages of conservation methods implemented in China, and while certain methods, such as moratoriums on aquaculture, show significant advantages, others, such as the establishment of protected habitats, have limitations due to incomplete findings. These methods provide a solid foundation for the conservation of the Tachypleus tridentatus, and also point to possible future directions, such as the implementation of polyculture. However, there is a need to improve the efficiency of existing methods through further development and additional data collection studies. To address the acknowledged limitations and gaps in this study, additional exploration and discourse are imperative to advance the preservation of Tachypleus tridentatus.

Hatchery capacity needed to support large‐scale Atlantic surfclam fishery enhancement

AbstractFishery enhancement methods are being explored globally to sustain commercial and recreational fisheries through improving the productivity and management of marine populations impacted by anthropogenic stressors. It is expected that access to important Atlantic surfclam fishing grounds will be limited or lost due to growing overlap with offshore wind energy development. This study explores the economic viability of large‐scale hatchery production to improve fishery access and potentially offset additional costs, reduced revenues and potential job losses associated with the displacement of the fishing fleet. Reports and primary literature were used to understand the growth and survival of Atlantic surfclams in hatchery and nursery settings to calculate the scale of hatchery efforts needed to support one million (1M) bushels of fishery‐sized clams (&gt;120 mm). Data on labour, energy, construction and material inputs and costs for hatchery and nursery production were gathered by analysing available literature and information provided by hatchery managers, researchers and others knowledgeable about shellfish hatchery production. A techno‐economic cost model and Monte Carlo analyses were employed to explore average costs and their variability. This study suggests that 374M–2.1B Atlantic surfclams are needed at the end of the hatchery stage to produce 1M bushels of market‐sized product. Total production costs range from $3.7 to $15.1M, including $2.9–$13.3M in hatchery costs and $800K–$1.9M in nursery costs. Under current market conditions, where Atlantic surfclams regularly sell for $14–$17/bushel, this analysis suggests that hatchery production could be considered a viable fishery enhancement method that supports human access to the fishery, though several additional questions remain.

An insight into the fishery, biology and population dynamics of Auxis rochei (Risso, 1810) along the south-west coast of India

Auxis rochei is one of the coastal tunnies contributing substantially to the tuna landings inIndia, with an average (2014-2019) annual catch of 7210 t. Kerala stood first, with an annualaverage landing of 3176 t. The fishery comprised 14.5 - 39.6 cm fork length (FL) size groupswith a mean length of 27.64 cm and a major mode of 26 cm FL. The Length-weight (L-W)relationship of pooled fishes was expressed as W= 0.000003 L3.22 (r2= 0.91). The size at firstmaturity was estimated at 25.8 cm FL when the fish was 1.5 years old. The number of eggsper spawning ranged from 84,562 to 1,33,698 and the ova diameter ranged between 0.1and 0.6 mm, indicating asynchronous oocyte development with multiple spawning. Highergonadosomatic index (GSI) was recorded during April, May and June and coincided withthe minimum gastrosomatic index (GaSI). The recruitment pattern was bimodal, with variedintensity ranging from 0.79-17.89%. Growth was allometric and the von Bertalanffy growthequation derived was Lt=43.5(1-e-0.8(t+0.0212)). The growth performance index (ɸ) was 3.18 andthe longevity of the fish was estimated at 3.7 years. One-year-old plus fishes sustained thefishery (22 - 32 cm FL). Total mortality (Z), natural mortality (M) and fishing mortality (F)were estimated at 3.70, 1.40 and 2.30, respectively, with an exploitation rate (E) of 0.62and the exploitation ratio (U) of 0.60. Beverton and Holt yield per recruit (Y/R) and Biomassper recruit analysis indicated that the Emax was at 0.87, much higher than the present levelof exploitation, reflecting the sustainable fishery along the coast. Standing stock biomass(SSB) was estimated at 7215.7 t, and the spawning stock biomass formed 55.5% of the SSB.Thompson and Bell analysis indicated the MSY as 8125 t, at F-factor, 2.6. The biologicalreference points FCURR/FMSY (0.4) and BCURR/BMSY (1.5) were at safe levels, signifying the scopefor fishery enhancement. Keywords:Biological reference point, Fecundity, Growth, GSI,L-W relationship, Mean length, Mortality, SSB

Fisheries Enhancement after Hydrological Intervention in Chilika Lagoon and Strategies for Responsible Management

Chilika lagoon situated in the state of Orissa on the east coast of India is a hotspot of aquatic biodiversity including fish germplasms. Fishery yield from the lagoon contributes 71% to the total economic valuation of the ecosystem. The ecosystem suffered rapid degradation during the last few decades due to anthropogenic pressure and natural changes. Fish yield from mid-eighties onwards until hydrological intervention made by Chilika Development Authority during September, 2000 showed declining trend, registering lowest ever landings of 1274 t during 1995-96 and 1746 t in 1999-2000, immediately before opening of the new lagoon mouth. The opening of artificial mouth by dredging the sand spit reduced the 1ength of outer channel by 18 km. The hydrological intervention has resulted in many positive impacts such as spectacular increase in fishery yield and biodiversity, improvement in overall salinity regime, natural eradication of freshwater weeds, flushing out of silt etc. Sudden increase in fishery yield during 2000-01 immediately after opening of the new mouth registered 185.42% increase over the pre-mouth base year (1999-2000) and an all time high yield of 11,988.88 t during 2001-02, showing 586.74% increase over the base year has been recorded whose economic valuation was estimated at Rs.571.6 million. The average fishery yield for three years (2000-01 to 2002-03), economic valuation of fish catch, fishery diversity, migratory fish component, commercial fish groups, average productivity, per capita income and catch per unit effort (CPUE) during the post-mouth period registered 432.06%, 621.47%, 19.85%, 7.20%, 42.86%, 482.59%, 373.15% and 432.27% increase, respectively over the base year, 1999-2000.

High trophic similarity between non-native common carp and gibel carp in Turkish freshwaters: Implications for management

Although the detrimental ecological and economic effects of introducing freshwater fish species have been extensively documented, non-native freshwater fishes continue to be introduced in large numbers globally to enhance fisheries and aquaculture. In Turkey, stocking of common carp Cyprinus carpio is practised to provide food security for people and job security for artisanal fishers, resulting in a country-wide distribution. These stockings, however, increase the risk of accidental introductions and have led to introductions and subsequent invasions of gibel carp Carassius gibelio, a globally invasive and highly detrimental fish species. Here, we assessed the growth types, body conditions and trophic interactions via bulk carbon and nitrogen stable isotope analysis of common and gibel carp in both natural and artificial water bodies in Turkey. The results indicated that common and gibel carp express similar growth types and body conditions in all waters and have similar trophic ecologies. This leads to substantial trophic niche overlaps in waters where they co-occur, with the potential for strong interspecific competition. Considering the ongoing stocking of common carp for fishery enhancement, we recommend to specifically target these stockings in waters where gibel carp has already become invasive. Our findings, indeed, suggest that common carp releases have the potential to hamper invasive gibel carp populations by increasing the competitive interactions between the two species.

Implications of habitat use and movement of stocked juvenile dusky flathead (Platycephalus fuscus) on stock enhancement release strategies

AbstractStocking of marine fish into coastal systems to augment natural recruitment is a growing practice adopted by fisheries managers around the world. Releasing fish directly into well‐resourced nursery grounds greatly increases survival and retention of stocked individuals but requires an understanding of juvenile habitat requirements. In eastern Australia, the dusky flathead (Platycephalus fuscus) is a highly regarded recreationally targeted species and the focus of an emerging stock enhancement programme, although little is known of their specific nursery habitat. Using acoustic telemetry, hatchery‐reared juveniles were monitored in Lake Macquarie to quantify habitat use and dispersal. Sandy areas adjacent to edges of seagrass beds were favoured, likely as foraging habitat. Within 5 weeks after release, fish were detected 5 km from the release site, but only at locations containing seagrass beds, so stocked fish likely disperse around estuaries to regions with suitable habitat. Future releases of dusky flathead should target areas containing patchy seagrass‐sand to optimise stocking outcomes. Beyond fisheries enhancement programmes, our findings highlight the importance of structured habitat, such as seagrass beds, for juvenile fish.

Assessment of habitat and reef fish population characteristics in Pari Island cluster waters Seribu Archipelago Indonesia

The Pari Island Cluster, located on the Southside of the Seribu Archipelago, is bordered by Jakarta and Tangerang Regency is covered Pari, Kudus, and Tikus Islands. The Pari Island cluster has potential ecosystems, such as coral reefs, seagrass, and mangrove. The presentation of this article is an overview of the results of research conducted by the Research Institute for Marine Fisheries and the Research Institute for Fisheries Enhancement, The Agency for Marine and Fisheries Research and Human Resources. This study aims to present and describe habitat and reef fish populations. The assessment result shows that the criteria for the coral reefs’ health were poor to good, mostly moderate, the best in the southeast and northeast waters, which had been designated MPAs. Reef fish population density on the criteria was very rare or low at all observation sites. The dominant group was Caesio cuning, Cephalopholis boenak, Scarus ghobban (target group), and Chaetodon octofasciatus (indicator group). The implementation hopes Pari Island Cluster waters would expand to be designated MPAs due to the large number of care areas used for fishing territories.

Genomic analyses indicate two blue swimmer crab species in Australia, evidence for natural interspecific hybridization and genetic structure within species with implications for fisheries management and stock enhancement

Blue swimmer crab species are widely distributed in Indian and west Pacific Oceans including the coastline around Australia and have been identified as potential candidates for stock enhancement. A recent taxonomic review revealed the presence of two blue swimmer crab species in Australia, namely Portunus armatus which is found around most of the Australian coastline, and Portunus pelagicus which is found in the northern coast where it is sympatric with P. armatus. It is important to understand population structure and genetic diversity of Portunus spp. to efficiently manage stocks. In the present study we investigated species classification and population structure of Portunus spp. in Australia using full and partial genomic information, namely mitochondrial COX1 gene sequences derived from whole genome sequencing and single nucleotide polymorphic (SNP) markers developed from partial genome sequencing. Blue swimmer crab samples were collected from the western (n = 52), northern (n = 17) and eastern (n = 110) coasts of Australia. Genetic diversity and population genetic structure were assessed for within and between region variation. Our genomic results indicated the presence of two blue swimmer crab species in Australia. One, namely, P. pelagicus was found only in Northern Territory (Darwin), and other, namely P. armatus was found around Australia. There was evidence of natural hybridisation between two species in Northern Territory (Darwin) where they were sympatric. P. armatus populations from the western, northern and eastern regions were genetically different although there were no significant genetic differences observed between the Queensland and New South Wales populations nor between the two neighbouring populations in Western Australia. Results found in the present study supports the view that the P. armatus populations in western, northern and eastern regions of Australia should be treated as at least three different stocks. A lack of genetic structuring along the eastern coast suggests blue swimmer crabs can be considered as a single stock along the sampled range at least in relation to fisheries enhancement, release programs and broodstock management.

Closing the life‐history loop: Density effects on fecundity and egg size of an exploited, amphidromous fish (Galaxias maculatus) in freshwater protected areas

AbstractUnderstanding how fecundity and egg size respond to density‐dependent and density‐independent processes is essential for fisheries assessments because it shows managers how exploited populations respond to fishery closures. Similarly, the extent to which density‐dependent and density‐independent processes influence fecundity and egg size in freshwater protected areas (FPAs) is important for determining their conservation potential and effectiveness as a fisheries enhancement strategy.The fecundity and egg size of 164 sexually matureGalaxias maculatusfemales collected from coastal waterways on the West Coast of New Zealand's South Island were determined from a combination of techniques. Specifically, the additive and interactive effects of density, temperature, and body size on fecundity and egg size were examined in 10G. maculatuspopulations across a density gradient mediated by fishery closures and tested for an egg size/fecundity trade‐off.There was no evidence of an egg size/fecundity trade‐off, or of negative density‐dependent effects on fecundity or egg size within FPAs. Egg size, gonadosomatic index, and water temperature were correlated with latitude.Fecundity increased with body size, but egg size did not. This highlights the importance of available forage (terrestrial‐ and stream‐based prey) forG. maculatusto maintain individual growth to increase egg production and larval export derived from no‐take FPAs.For the current network of no‐take FPAs to be more effective as a management tool, efforts should focus on the remediation of in‐stream and requisite riparian spawning habitats, the degradation of which has caused population bottlenecks for this culturally and economically important amphidromous species. The major subsidy from FPAs for theG. maculatusmetapopulation is sustainable egg production if migration to sea of the greatest possible number of larvae can be ensured.

Review of the Southern Ocean Sanctuary: Marine Protected Areas in the context of the International Whaling Commission Sanctuary Programme

This scientific review of the Southern Ocean Sanctuary (SOS) was commissioned by the IWC Scientific Committee and presented to the IWC Steering Committee on 27-28 June 2004. This review addresses a number of questions related to the effectiveness of the SOS and provides recommendations on how to incorporate Marine Protected Area (MPA) concepts into the SOS and the IWC Sanctuary programme. Overall, the SOS – and IWC Sanctuaries in general – are based on vague goals and objectives that are difficult to measure, lack a rigorous approach to their design and operation and do not have an effective monitoring framework for evaluation. In particular, the SOS represents a ‘shotgun’ approach to conservation, whereby a large area is protected with little apparent rationale for boundary selection and management prescriptions within the sanctuary. While a vast array of ecosystem-level and precautionary conservation benefits have been invoked for the establishment of the SOS, in reality this sanctuary does little more than provide a false sense of security by assuming that broad protections for whale populations are in place. The SOS was designed to restrict commercial harvests from the low latitude feeding grounds occupied by large whales during the austral summer. However, the SOS does not protect against or mitigate other threats to Southern Ocean whale stocks and the marine ecosystems upon which these populations depend, including pollution, habitat degradation and loss, introduced species and global climate change. We thus contend that sanctuary establishment and evaluation should be guided by a series of measurable and tangible goals, aimed at quantifying the status of both the ‘protected’ species under consideration and their role in the broader marine ecosystem. In particular, the SOS could be improved substantially to become an important part of IWC management and the larger conservation of Southern Ocean marine ecosystems, if the following steps were implemented: (a) development of formally stated goals (e.g. biodiversity protection, fisheries enhancement); (b) establishment of measurable objectives with which to assess progress towards attaining these goals; (c) creation of a formal management plan, including the establishment of a monitoring framework; and (d) development of more appropriate review criteria, reflecting the ecological objectives of the management plan.

From Africa to the world—The journey of Nile tilapia

AbstractDespite the fact that Nile tilapia (Oreochromis niloticus) (Linnaeus, 1758) are African freshwater fish, they have been introduced into many countries inside and outside Africa. The journey of Nile tilapia started during the second half of the 20th Century, especially in Southeast Asia and the Americas, mainly for aquaculture and fisheries enhancement. Most of these introductions became well established in aquaculture. As a result, aquaculture of Nile tilapia has been steadily expanding in many countries. These fish play an important role in the livelihoods of local societies on different continents. This review summarizes the current knowledge on global Nile tilapia introductions and sheds light on their social and economic contributions to the countries into which they have been introduced, as well as their share in the global fish market. The ecological impacts of tilapia introductions have also been addressed. The success stories of the major Nile tilapia producers were highlighted so that the lessons learned from their experiences could be transferred to other countries.

Effects of temperature on metabolic rate and lower dissolved oxygen tolerance of juvenile speckled peacock bass Cichla temensis.

The speckled peacock bass Cichla temensis is a popular sport and food fish that generates substantial angling tourism and utilitarian harvest within its range. Its popularity and value make this species important for management and a potential aquaculture candidate for both fisheries enhancement and food fish production. However, little is known of optimal physiochemical conditions in natural habitats, which also are important for the development of hatchery protocols for handling, spawning and grow-out. Speckled peacock bass have been documented to have high sensitivity to extreme temperatures, but the metabolic underpinnings have not been evaluated. In this study, the effects of temperature (25, 30 and 35°C) on the standard metabolic rate (SMR) and lower dissolved oxygen tolerance (LDOT) of juvenile speckled peacock bass (mean ± standard error total length 153 ± 2 mm and wet weight 39.09 ± 1.37 g) were evaluated using intermittent respirometers after an acclimation period of 2 weeks. Speckled peacock bass had the highest SMR at 35°C (345.56 ± 19.89 mgO2 kg-1 h-1 ), followed by 30°C (208.16 ± 12.45 mgO2 kg-1 h-1 ) and 25°C (144.09 ± 10.43 mgO2 kg-1 h-1 ). Correspondingly, the Q10 , or rate of increase in aerobic metabolic rate (MO2 ) relative to 10°C, for 30-35°C was also greater (2.76) than from 25 to 30°C (2.08). Similarly, speckled peacock bass were the most sensitive to hypoxia at the warmest temperature, with an LDOT at pO2 of 90 mmHg (4.13 mg l-1 ) at 35°C compared to pO2 values of 45 mmHg (2.22 mg l-1 ) and 30 mmHg (1.61 mg l-1 ) at 30 and 25°C, respectively. These results indicate that speckled peacock bass are sensitive to temperatures near 35°C, therefore we recommend managing and rearing this species at 25-30°C.

Examining current best-practices for the use of wild post-larvae capture, culture, and release for fisheries enhancement

Demand for marine fisheries is rising despite global impacts on the productive capacity of wild fish stocks due to overfishing, habitat loss, and global warming. Fisheries enhancement programs—aimed at augmenting stocks by releasing juveniles into the wild—are expected to play an increasingly important auxiliary role in addressing capture-based fishery limitations into the future. However, concerns exist over the impacts and efficacy of aquaculture-based enhancement (ABE), releasing captive-bred fish into wild populations. An alternative but understudied approach for fisheries enhancement is wild post-larvae capture, culture, and release (PCCR). Here, we provide an overview of the PCCR process, from initial planning to measuring success, providing an overview of its implementation in a viable finfish fishery, the white seabream Diplodus sargus in the Mediterranean. We discuss management application of PCCR-based enhancement and its limitations, highlighting existing knowledge gaps and future research required to realize the full potential of this alternative approach. Notwithstanding some limitations–including limited uptake for full evaluation, some species restrictions, density-dependent mortality, and the remaining open challenge for stock enhancement generally of tracking released fish through to reproduction–PCCR offers potential as a credible auxiliary management tool for fisheries restoration.

Application of artificial spawning substrates to support lacustrine fish recruitment and fisheries enhancement in a Chinese lake

Lake littoral zones with abundant submerged vegetation are considered to harbor diverse biotic communities and additionally serve as spawning grounds for important fishery resources. In recent decades, due to various human activities submerged vegetation in lakes have declined dramatically resulting in the function loss of spawning grounds. In order to enhance the recruitment of lacustrine fish (mainly Carassius auratus and Cyprinus carpio) and the proliferation of fishery resources, we explored a method of constructing artificial spawning ground based on artificial spawning substrate in lake. The results of present study indicate that the artificial substrates with complex and dense three-dimensional structure which have enough space to enable material exchange and oxygen circulation could be efficient to enhance fish recruitment. The water temperature of spawning peaks of artificial substrates were within the range of 20 ~ 25°C, and the water temperature provides a basis for the deployment period of artificial spawning grounds. The spawning substrate in the upper layer of water column was more attractive for fish to spawn. The above results provide guidance for the deployment of artificial spawning grounds from both temporal and spatial scales. Observations on the behavior of aggregations found that spawning activities mainly occurred at night and in the early morning. The abundance of larger individuals (&amp;gt;20 cm), as potential spawning groups, increased during this period. The above findings are informative to the construction and management of artificial spawning ground in lakes.