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There is an increasing concern about welfare issues related to battery cages, which are commonly used in Vietnam, and requires a modified cage that improves hen welfare while retaining its economic and management advantages. We combined adjacent conventional cages to form group cages to examine the effects of stocking density on egg production, economic returns, and aggressive pecking of hens. The control group included triplicate conventional cages with four birds/single cage (12 hens per three cages) or 450 cm2 area per hen. Three group cage treatments were set up with 10, 12, and 14 birds per group cage or 540, 450, and 386 cm2 of floor area per hen, respectively. Compared to 14 birds per cage, hens housed at 10 birds per group cage had a higher hen-day production, consumed less feed, and thus had a better feed conversion ratio/dozen eggs. Reducing the stocking density to 10 birds per group cage resulted in additional production cost, but it was compensated for by a high egg income, and significantly decreased aggressive pecks. Group cages benefit hen performance, profitability, and welfare when decreasing the stocking density to 10 birds per cage with 540 cm2/hen. [ABSTRACT FROM AUTHOR]

The U.S. catfish industry is evolving by adopting intensive farming practices such as intensively aerated ponds and split-pond systems. The functional relationship between fish yield and key production inputs in these intensive systems was analyzed based on commercial catfish production data from 143 pond observations (2010−2018). A Cobb-Douglas production function was employed for the intensively aerated ponds and a modified translog production function was used to define the production relationships in split ponds. Results indicated that the size of fingerlings at stocking, stocking density, aeration rate, feeding rate, survival, and harvest size of the fish were statistically significant variables influencing fish production in intensively aerated ponds. Initial fingerling stocking biomass (interaction of stocking size and stocking density), feed conversion ratio (FCR), feeding rate, and pond size were the most important variables influencing production in split-pond systems. Feed fed, as well as stocking biomass, were the significant variables found in both models. Both production functions indicated further scope for improvement in the use of inputs to increase production, especially in feed management. [ABSTRACT FROM AUTHOR]

Dust in feedlots is detrimental to optimal cattle performance. Contributors such as climate, manure production, and animal behaviour can affect dust production and ultimately, cattle health. Bovine respiratory disease (BRD) and acute interstitial pneumonia (AIP) represented to 68% of death loss across 30 feedyards from 2015 to 2017. Bovine respiratory disease specifically costs producers between $800 and $900 million each year with the cost per animal varying based on number of treatments, occurrence, and performance differences. Altering feeding schedule, stocking density, and sprinkler systems have decreased dust concentrations. By using these methods, cattle feeders can limit dust production and promote animal health. This paper serves to consolidate previous research and data discussing the effects of dust on cattle health. [ABSTRACT FROM AUTHOR]

African catfish, Clarias gariepinus (B.), a scale-less fish, is prone to be wounded due to high stocking density, predation, territorial protection, and so on. This wound could serve as an entry point of pathogens causing biological and economical losses if not well managed. Therefore, the present study evaluated the wound healing potentiality of clove, Eugenia caryophyllata, buds extract (ECBE) on artificially wounded African catfish. Four isonitrogenous diets (40% crude protein) were prepared to contain ECBE at levels of 0.0, 5.0, 10.0, or 15.0 g/kg diet. Fish (61.5 ± 2.51 g) were lacerated (1 cm long) in both caudal and lateral regions and allotted to 12 rectangular tanks in a completely randomized design. The fish were fed on one of the experimental diets in triplicates for 14 days while observing the wound healing closure and histological changes. Fish fed ECBE-supplemented diets had better healing rates and percentage faster than that fed the control diet. The wound healing rate and percentages were delayed in fish fed control and lower levels of ECBE diets. However, fish fed a diet containing 15 g ECBE/kg diet achieved total/highest healing (100%) on the 12th day post-wound (dpw) in lateral and 10th dpw in caudal regions, while the least healing rate (6.29%/day) and percentage (88%) were obtained in fish fed the control diet in lateral and caudal regions in 14 dpw. Furthermore, the wound was been healed faster in the caudal region than the lateral one with earlier tissue regeneration and normal aligned keratinocytes of the epidermal layer and muscle layer. Therefore, the inclusion of 15 g ECBE/kg diet in diets for African catfish could be used in fish farming to achieve faster wound healing and to avert mortality and infection associated with wounds. [ABSTRACT FROM AUTHOR]

1. The effects of housing system and stocking density on growth performance and carcase yield of a commercial strain of broiler chickens reared under tropical environmental conditions may differ from temperate conditions. 2. In two experimental periods, carried out during two contrasting seasons of the year (winter and summer), 240 Cobb 500 male chickens were randomly assigned in groups of 60 to 1 of 4 treatments, with 6 replicates in each, low stocking density with outdoor access (LO, 5 birds/m2); high stocking density with outdoor access (HO, 10 birds/m2); low stocking density indoors (LI, 5 birds/m2); high stocking density indoors (HI, 10 birds/m2). From 21 to 42 d old, body weight (BW) and feed intake (FI) were weekly recorded. Mortality was measured daily and carcase weight at slaughter. Indoor and outdoor temperature and relative humidity were measured daily. 3. There was a tendency for chickens raised in the outdoor access to be heavier than those raised in the indoor treatments. Chickens raised in the low-density treatments in the first experimental period were significantly heavier, gained more weight and had lower value for feed conversion ratio (FCR) than those reared at high density. In the second experimental period mortality significantly increased on week 4 due to heat stress. Birds raised with outdoor access had an increased carcase yield compared to those raised exclusively indoors. 4. In conclusion, low stocking density in combination with low environmental temperatures had enhancing effects on BW, BWG, FI and FCR, and the effects of housing system depended on stocking density. Low stocking density and outdoor access had positive effects on carcase yield. [ABSTRACT FROM AUTHOR]

Rainfall and stocking densities are key drivers of vegetation functioning and productivity in semi-arid regions. Below-average rainfall is of particular importance in the agricultural sector as it limits fodder availability for livestock in the short term, and can influence potential agricultural productivity through inducing the mortality of palatable perennial plant species in the long term. Changes in rainfall trends are not equal for all regions and must be quantified locally to sustainably manage natural grazing resources. The Upper Karoo has experienced considerable fluctuations in rainfall for many thousands of years, with relatively wetter and drier phases. This study analysed farm records from the past eight decades at eight sites in the Upper Karoo. The aim was to provide detailed and comparable descriptions to generate a more general understanding of rainfall at a spatial scale over this entire bioregion and to assess recent farming conditions within a historical rainfall context. A steadily increasing trend in rainfall of approximately 10 mm per decade has been observed in the Upper Karoo over the past eight decades, and the 30-year period from 1989 to 2018 was generally characterised by above-average rainfall. Presently, the farming conditions are more favourable compared to historical rainfall recorded before the year 1989. [ABSTRACT FROM AUTHOR]

Sia ME, Doyle RM, Moser KA. 2020. Recent trends in mountain lake primary production: evaluating the response to fish stocking relative to regional environmental stressors. Lake Reserv Manage. XX:XXX–XXX. Although mountain lakes are often remote, they are impacted by a myriad of stressors, including species introductions, atmospheric fertilization, and climate change. These stressors have the potential to increase primary production, which can threaten mountain lakes by decreasing water quality, reducing species richness, and lowering dissolved oxygen concentrations. The relative importance of these stressors as drivers of production is not well understood. We therefore investigated the importance of fish stocking, relative to other stressors, as a driver of primary production in mountain lakes. Our research focused on Uinta Mountain lakes, which, like many lakes in the western United States, were stocked with salmonid fish in the 1950s. In 2 stocked lakes and one unstocked lake, we reconstructed a record of ∼300 yr of primary production from lake sediments using changes in percentage of organic matter and spectrally inferred concentrations of chlorophyll a and its derivatives. With long-term trends in primary production, we determined that all 3 study lakes, including the unstocked lake, show unprecedented increases in primary production beginning in the 1950s. We attribute recent increases in primary production mainly to atmospheric deposition of nitrogen and climate warming, but do not rule out future impacts of fish stocking. Our article demonstrates how breakpoint analysis can be used to identify the most serious threats to mountain lakes, even if those lakes are impacted by multiple stressors or stressors originating from distant places. [ABSTRACT FROM AUTHOR]

Stocking game fish into originally fishless mountain systems is a major threat for high-altitude lakes and the inhabiting native species. A history of ecological and cultural barriers The existence of downstream barriers to fish colonisation facilitates the eradication of alien fish from mountain lakes but there are cultural barriers which make it difficult to adopt even basic conservation measures. Fish have been introduced into significant proportions of mountain lakes (usually > 50% of lakes larger than 0.5 ha; Ventura et al. [28]) resulting in a regional - or global - threat that could pose the main threat to biodiversity in European mountain lakes (Fig. [Extracted from the article]

South Africa is in the process of developing a National Freshwater (Inland) Wild Capture Fisheries Policy. A properly focused research strategy is essential to guide the policy development process, and thus a dedicated 'Inland Fisheries' workshop was convened by the South African Society for Aquatic Scientists in June 2018 to update and further develop a list of priority knowledge requirements for inland fisheries in the country. The main themes that emerged during the workshop were developed and contextualised as ten research questions. These were: (1) What is the exploitation potential of inland fisheries? (2) What are the health risks from consuming freshwater fishes? (3) Who currently uses inland fisheries and what are their harvests? (4) What can we learn from historical constraints to inland fisheries development? (5) How will governance of fisheries have to change in an evolving sectoral environment? (6) What are the options for fisheries enhancement? (7) What are the most appropriate fisheries technologies? (8) What value chains and employment opportunities are associated with inland fisheries? (9) What is the impact of water level fluctuations on fish production? (10) What are the impacts of pathogenic diseases on fish populations? [ABSTRACT FROM AUTHOR]

Chraïbi VLS, Fritz SC. 2020. Assessing the hierarchy of long-term environmental controls on diatom communities of Yellowstone National Park using lacustrine sediment records. Lake Reserv Manage. 36:278–296. An ecosystem's ability to maintain structure and function following disturbance, defined as resilience, is influenced by a hierarchy of environmental controls, including climate, surface cover, and ecological relationships that shape biological community composition and productivity. This study examined lacustrine sediment records of naturally fishless lakes in Yellowstone National Park to reconstruct the response of aquatic communities to climate and trophic cascades from fish stocking. Sediment records of diatom algae did not exhibit a distinct response to fish stocking in terms of assemblage or algal productivity. Instead, 3 of 4 lakes underwent a shift to dominance by benthic diatom species from 1935 to 1950, which suggests lower lake levels resulting from warmer, drier climatic conditions. The lake that did not undergo such a shift is fed by groundwater rather than snowmelt, suggesting a buffering effect by water source. Dissimilarity analysis shows that the diatom assemblages in all 4 lakes have become increasingly dissimilar since circa 1955, suggesting that communities have not yet stabilized from the first-order influence of climate. Thus, climate likely had a more prominent influence on diatom community structure than did manipulation of the fish community. Understanding the relative importance and interplay among abiotic and biotic stressors and the resultant resilience of an ecosystem provides implications for the adaptive management of lakes. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) from poultry production facilities may strongly affect the health of animals and workers in the houses, and PM emitted to the ambient air is an important pollution source to the surrounding areas. Aviary system is considered as a welfare friendly production system for laying hens. However, its air quality is typically worse as compared with conventional cage systems, because of the higher PM concentration of indoor air and other airborne contaminants. Furthermore, PM's physical property, which has a direct impact on the penetration depth into the lungs of the birds and humans, is largely unknown for the aviary system. Therefore, a systematic method was utilized to investigate the characteristics of particles in the aviary house with large cage aviary unit system (LCAU) in Beijing, China. For the field measurements, three measuring locations were selected with two inside and one outside the house with LCAU to continuously monitor PM concentrations and collect the samples for particle size distribution (PSD) analysis. Results showed that PM2.5, PM10, and total suspended particulate (TSP) concentrations averaged at 0.037 ± 0.025 mg/m3, 0.42 ± 0.10 mg/m3, and 1.92 ± 1.91 mg/m3, respectively. Particle concentrations increased from October to December due to less ventilation as the weather got colder, and were generally affected by stocking density, ventilation rate, birds' activities, and housing system. Meanwhile, indoor PM2.5 concentration was easily impacted by the ambient air quality. Mass median diameter (MMD) and mass geometric standard deviation (MGSD) of the TSP during the measurement were 18.92 ± 7.08 μm and 3.11 ± 0.31, respectively. Count median diameter (CMD) and count geometric standard deviation (CGSD) were 1.94 ± 0.14 μm and 1.48 ± 0.08, respectively. Results indicated that the aviary system can attain a good indoor condition by suitable system design and environment control strategy. Implications: Indoor PM2.5 concentration of the layer house can be significantly affected by ambient air quality when the air quality index (AQI) was larger than 100. PM2.5 and PM10 concentrations of the layer house with a LCAU system were comparable to the cage system. TSP concentration was higher, and PM size was larger than most of the cage system. System design, larger space volume, and higher ventilation rate were the main influence factors. Good indoor environment of the aviary system can be achieved through the reasonable design of the production system and appropriate environment control strategy. [ABSTRACT FROM AUTHOR]

Seed dispersion is a critical process to vegetation dynamics which is particularly complex in mosaic-like landscapes as the Pantanal wetlands. We analyzed some aspects of ichthyochory in the Pantanal flooded grasslands. The fish were collected and had their whole intestinal contents removed and submitted to suitable germination conditions for 179 days. We collected 661 specimens belonging to 40 species. Feces from Astyanax lacustris, Poptela paraguayensis, Moenkhausia sanctafilomena and Moenkhausia bonita produced 15 seedlings of herbaceous plant of the species Ludwigia inclinata, Ludwigia leptocarpa and a non-identified monocotyledon. A total of 30.4 g of fecal mass was recovered with a rate of 0.49 seedling.gram−1. There is a positive relation between the number of seedlings obtained and the amount of fish fecal mass (g). Currently, Pantanal landscape dynamics is under rising pressure of field compartmentalization due to man-made roads which restrains fish transit. [ABSTRACT FROM AUTHOR]

Striped catfish (Pangasianodon hypophthalmus) fingerlings were stocked (60 fishes/m3) in cemented square tanks for ornamental fishery purposes at the College Fish Farm in Mangalore. A total of 400 fishes with a mean weight (g) ranging from 3.24 ± 1.21 to 6.70 ± 1.13 and a mean length (cm) of 7.50 ± 0.94 to 9.50 ± 1.10 were examined. A severe outbreak of salt-like granule white spots was found on the body surface. Ichthyophthirius multifiliis, a ciliate pathogen, was identified as the causative agent by clinical signs, wet mount, and histopathological observations. Infected fishes were transferred and equally distributed to the 0.45 m3 glass aquaria and treated with three treatments: (T1) methylene blue + salt; (T2) raising temperature with salt; and (T3) formalin + malachite green. The best fingerling survival (55 ± 9.36%) was obtained by elevated water temperature with salt in T2. [ABSTRACT FROM AUTHOR]

Resources utilization and trophic structure in aquatic food webs play important roles in the ecosystem stability and functioning. Silver carp (SC, Hypophthalmichthys molitrix) and bighead carp (BC, Hypophthalmichthys nobilis) are intensively stocked in lakes and reservoirs in China and share similar food resources and trophic positions in water bodies. To better understand the ecological roles of SC and BC in natural freshwater, two mesotrophic reservoirs (Nanwan and Nianyushan) were selected to compare resource utilization and the trophic niche of these two fish species. Data analysis using Bayesian mixing model showed that SC was more like a fine particulate organic matter (fPOM) feeder, while BC consumed more coarse particulate organic matter (cPOM) and displayed a higher trophic position in both reservoirs. In contrast, niche breadths represented by the corrected standard ellipse area (SEAC) were essentially the same for SC and BC in Nanwan (SEAC = 6.1 for SC and BC), but much larger for silver carp in Nianyushan (SEAC for SC: 11.6, SEAC for BC: 4.2). The high stocking ratio of SC/BC in Nianyushan was the probable reason for the large SEAC of silver carp, which suggested that silver carp could use more food resources and become more competitive with a higher stocking biomass ratio. The results indicated that the trophic partitioning of filter feeders might be regulated by the stocking biomass ratio of the fish to some extent. [ABSTRACT FROM AUTHOR]

Hyperspectral images contain both spectral and spatial image information and were investigated to characterize the freshness of fish. However, most studies of this application have focused on spectral signals rather than image features. The goal of this work was to investigate the ability of spectral and image textural variables for predicting the chemical and physical qualities of fish, respectively, and to optimize the variables for the specific quality determination. The chemical (total volatile basic nitrogen, TVB-N) and physical (texture profile analysis, TPA) properties were investigated. Partial least square (PLS) was applied to develop fish quality prediction models with the spectral and textural variables from the hyperspectral images. The results showed that the TVB-N content of fish fillets was accurately predicted using the spectra. Meanwhile, the TPA parameters were determined through the image textural features with high accuracy, which indicated image textural features were highly related with the TPA parameters. Moreover, spectral and textural features were also extracted from fish eyes and gills and were further used to predict the intact fish quality, taking advantage of the freshness sensitivity of the eyes and gills. The results illustrate that spectra from fish eyes and gills are a potential tool to predict the TVB-N content and TPA parameters for intact fish. [ABSTRACT FROM AUTHOR]

The inward displacement perpendicular to the body surface produced by external pressure is an important index to evaluate the pressure comfort and optimal design of apparel products. In this paper, we studied on the functional relationship of pressure, displacement and angle when the body was in dynamic state after dressing. The dynamic pressure was divided into two parts: pressure with time (instantaneous, 1, 2, 4, 8 and 12 h) and pressure with movement (walking which described as upright position, leg lift 10°, leg lift 30° and foot backward off the ground). The displacement of each point on the lower leg cross section in four stages of walking process and six periods of time were simulated by ANSYS finite element software. After fitting, the functional curves between pressure/displacement ratio and the angle were obtained. By comparing, we found out that all the curves were presented nearly complete uniform curving form no matter what state of the human body was in. That is, when the human body was under clothing pressure, the corresponding displacement value on the body surface can be calculated on the premise of the known pressure value at any point of lower leg cross section during the wearing process by functional equation. All these solutions supplied a theoretical reference for optimal design of the top part of men's socks. [ABSTRACT FROM AUTHOR]

Different values have resulted in conflicts between anglers and conservation lobbies in the management of trout in South Africa. Key to the conflict is the demarcation of boundaries to areas in which brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss currently occur, or are likely to establish following stocking for angling. To provide a longer-term perspective on these areas, we developed models to link salmonid biological thermal thresholds to elevation. These, when applied spatially using a digital elevation model with a probability of occurrence model, provided the basis for estimating potentially available thermal habitat for these two cold water species. Here, we acknowledge that other variables (stocking history; river connectivity) also play a role in understanding trout distributions. Using a simple scenario of an increase in mean daily water temperatures of 2 °C, we demonstrated that both brown and rainbow trout are likely to exhibit considerable range reductions in the future. Because it is possible that these range restrictions will result in an increasing desire to introduce trout into areas above their current distribution limits for the maintenance of angling opportunities, conservation managers should prioritise these areas, with management interventions seeking to understand what will help to limit introductions. [ABSTRACT FROM AUTHOR]

Poor swimming performance and low hypoxia tolerance have been suggested as the main reasons for the dramatic decrease in the wild population of Chinese sucker. The present study aimed to investigate the potential for exercise training to enhance swimming performance and hypoxia tolerance in this fish species targeted for stocking enhancement. Fish were exercise trained (force to swim against a flow) once daily, twice daily or not exercise trained for 20 d and then detrained for 10 d (a period of nontraining). Training showed no significant effect on anaerobic swimming performance.. The fish from both training groups showed lower hypoxia tolerance and a lower survival rate under predation. Thus, the present study suggested thatexercise training showed little effect or even a negative effect on physiological function in Chinese sucker, and the forced training might not be the proper protocol to apply for improving the stocking enhancement of Chinese sucker.. [ABSTRACT FROM AUTHOR]

This study aims to clarify some aspects of the growth of Atlantic bluefin tuna, Thunnus thynnus (L.), (ABFT) mainly regarding parameters of the growth equation and of relative growth, in this case length-weight relationships. There is a great volume of literature on these matters and there is a danger that the resulting confusion may give rise to mistaken decisions. In spite of the publication of 55 articles on absolute growth (FL > 50 cm), which contain a total of 43 growth equations, no consensus has yet been reached within the ABFT assessment group (AG) of the SCRS on parameters such as Lmax and L∞. The results of the present study indicate that the L∞ = 314.9 cm of the growth equation used for the western stock by the AG from 2010 (Lt = 314.9 [1 - e-0.089 (t+ 1.13)]), which was discarded in 2016, lies within the confidence limits of the maximum Ls presented in this study (Lmax= 321.4 ± 8.7 cm), confirming that this equation fit the biology of the ABFT growth. With regard to the length-weight relationships, 38 articles (FL > 50 cm) have been consulted containing a total of 71 equations, but in spite of this the models adopted by the AG in 2014 underestimate the weight of spawners (>2 m) in high fattening phase by up to 23%. The coincidence of the length-weight model for the ABFT western stock, discarded by the AG in 2014, with that of Pacific bluefin tuna, Thunnus orientalis (T & S), (PBFT) indicates that both species must have the same growth, something that is not surprising since both were the same species until 2003. Other coincidences, such as the trend of condition factor K in adults and the growth in the first months of life, could ratify it. In the Pacific Ocean, where far fewer growth studies have been made on PBFT than on ABFT in the Atlantic and Mediterranean, the management of growth models for the purposes of stock assessment in the International Scientific Committee (ISC) makes more sense than that carried out by the SCRS on this matter. [ABSTRACT FROM AUTHOR]

This study assessed the effectiveness of a novel conservation strategy for the native brown trout populations in Sardinia (Italy). The conservation measures included: (i) installation of an electric fish barrier; (ii) removal of all the resident introgressed brown trout upstream from the barrier; (iii) restocking of the upstream region with native Sardinian trout genetically characterised; and (iv) estimation of native trout population size with prediction of future growth. Introgressed brown trout were removed using multiple-pass electrofishing methods in a 2-km region upstream from the barrier. In two eradication campaigns, conducted in 2010 and 2012, a total of 1801 trout were captured, comprising a total biomass of 55,501 g. The capture efficiency analysis showed total capture rates of over 99% were achieved for parr (0+ age cohort), and 100% for adult trout. After the eradication campaigns we restocked this area with native brown trout (Adriatic lineage, AD, according to the mitochondrial DNA control region nomenclature). The monitoring campaigns showed good survival (S = 60%) and reproduction of 3.1 recruits/adult trout. Successful breeding was recorded starting from the summer of 2015 and a self-sustaining population resulted after only two restocking events. The results of this restoration project allow recommendations to be made for future conservation eradication and repopulation projects for restoration of typical Mediterranean streams. [ABSTRACT FROM AUTHOR]

Gulf killifish, Fundulus grandis, is a hardy marine baitfish with established rearing techniques in ponds and static pools, but there is little information about the use of recirculating aquaculture systems (RAS) for growing killifish.The current trial investigated the effects of stocking density on growth and survival of young killifish in RAS. Young fish (28-day posthatch) of 51.6 ± 0.9 mg (mean ± SE) were stocked at 2, 5, 8, and 11 fish/L in 31 L tanks in RAS with triplicate groups for 16 weeks. Cannibalism was a major problem in the study, which increased with increasing initial stocking density, affecting survival negatively. Survival decreased (P < 0.03) with increasing initial stocking density and culture period. At the end of the trial, the 2, 5, 8 and 11 fish/L initial stocking density reduced to 1.66, 1.42, 0.86, and 0.74 fish/L respectively. A significant linear relationship existed between the initial stocking density and weight (y = 0.077x + 2.3; R2 = 0.8; P = 0.003), whereas an inverse relationship occurred between initial stocking density and survival parameters (y = −9.43x + 97.4; R2 = 0.89; P < 0.001). From the trial, the optimum density for culturing young of Gulf killifish in RAS appears to be around two fish/L. [ABSTRACT FROM AUTHOR]

The control and management of production factors have been of great economic interest for the aquaculture industry. In this study, the optimal harvesting time that maximizes the net benefits of shrimp cultured in freshwater was determined using a bioeconomic model fitted to six stocking density strategies (90, 130, 180, 230, 280 and 330 shrimp m−2). A model was constructed which included the size heterogeneity of the culture and the results obtained were compared with the traditional model which assumes size homogeneity for all individuals. The results from both models indicated that the stocking density of 90 shrimp m−2 was the best management strategy for optimizing net benefits. The economic importance of taking into account size heterogeneity in the culture of the white shrimp in freshwater is discussed. [ABSTRACT FROM AUTHOR]

Fish stocking is commonly used in developed countries and aims to improve recreational fish stocks and rebuild threatened species populations. Fish stocking is often contentious due to its high investment, limited scientific evaluation, and typically divided opinion from key stakeholders. Debates over the efficacy and effects of fish stocking continue to occur in the absence of key information about current and past practices, and their degree of alignment with the accepted responsible approach previously published in platform papers. Consequently, using Australia as a case study, this paper presents a framework for assessing fish stocking practices. First, recent fish stocking practices were benchmarked by compiling freshwater fish stocking statistics from every state and territory in Australia. Over 84 million fish were found to have been stocked in Australia between 2009 and 2015, with recreational species, both native and salmonid, comprising the majority of numbers and weight of fish stocked, respectively. Second, historical trends in fish stocking were assessed over a 106 year period across one major jurisdiction, finding significant changes in practices including a strong move toward native species, and a reduction in the number of salmonids stocked, but an increase in size. Third, a literature review was conducted to evaluate Australia's fish stocking practices and found they could be generally considered responsible, however improvements could be made in areas highlighted. This study provides a valuable framework to assess fish stocking practices, aiding our understanding, informing future discussion, and fostering better outcomes from this popular fisheries management tool. [ABSTRACT FROM AUTHOR]

The horse mackerels of the genusTrachurus(Pisces: Carangidae) are commercially important pelagic fish resources worldwide. There have been several studies of the parasites infecting fishes of this genus, the first one concerning the occurrence of the coccidianGoussia cruciataThélohan, 1892. Horse mackerels have been targeted in recent projects, in a number of countries that exploit this fish resource (Argentina, Chile, European and Mediterranean countries, North America), with a view of using parasites to define population structure, in conjunction with other methods and techniques, to achieve a better understanding of fish stocks and to minimize risks of localized extinctions. However, information on the occurrence of parasites in this fish genus is scattered through a substantial number of scientific journals, some of them of difficult access. The present review aims to compile the up-to-date knowledge on the occurrence of parasites of horse mackerels, from protozoans to metazoans, their distribution in diverse geographical areas, and to review and provide references to the studies of parasites as indicators of population structure. [ABSTRACT FROM PUBLISHER]

Giant clams are bivalves found across Indo-Pacific coral reefs and intensively harvested for both food and marine aquarium trade markets. Aquaculture protocols are well established, but there is very little data available on production and trade. This review compiled data from several international agencies and from each one of the 20 giant clam farms active in 13 countries in the Indo-Pacific. The findings show that the import/export data do not match, and that approximately 50% of internationally traded clams are aquacultured. Approximately 150,000 individuals were produced in 2015, mostly by private companies targeting the aquarium trade. Government hatcheries produced clams not only for the aquarium trade, but also for restocking and feeding local communities. However, production is still low and only three of the 20 farms collaborate with universities or research institutions and all of them reported production problems related to technical, commercial, infrastructure, and environmental issues. In order to fight such problems and optimize production, it is important that producers, universities, and government agencies throughout the world communicate with each other. [ABSTRACT FROM PUBLISHER]

The effects of high stocking density (HSD) on molecular, enzymatic, and biometric parameters of juvenile rainbow trout (Oncorhynchus mykiss) were compared to those of a low-density control group. The expression of genes related to growth, oxidative stress, and polyunsaturated fatty acid (PUFA) metabolism as well as antioxidant enzyme activities in the liver and muscle, the fatty acid composition of the whole fish and its growth parameters were determined in a control (10 kg/m3) and HSD group (39 kg/m3). At the end of a 60-day experiment: (1) Body weight change (BWC) decreased from 471.7% (control group) to 245.0% (HSD group); (2) Specific growth rate was 7.9%/day in the control group and 5.6%/day in the HSD group; (3) The level ofn-3 PUFA and docosahexaenoic acid, the ratio ofn-3/n-6 PUFA and mRNA expression of Δ-6 desaturase in the liver and muscle,sod1in the liver as well as elongase in the muscle increased in fish reared at HSD; (4) the mRNA transcript level of other genes in both tissues was down-regulated by HSD, except that ofsod1andgpx1in the muscle, which remained almost unchanged; and (5) HSD decreased antioxidant enzyme activities and the level of lipid peroxidation in both tissues. [ABSTRACT FROM AUTHOR]

Community-based natural resource management and nature-based tourism often go hand in hand to drive conservation and economic development in sub-Saharan Africa. However, the complementarity of the two strategies is controversially discussed in the literature. Built on survey data from 200 households conducted in 2012 we analysed the trade-off between conservation and development objectives by means of a mathematical programming model representing the economy of a rural conservancy in Namibia. We found that in the scenario describing unrestricted resource extraction, local communities mainly benefit from fishing and utilising forest products. In comparison, the scenario representing the social optimum, implying sustainably managed fish stocks and appropriate diets for community inhabitants, shows that community households increase agricultural diversification and shift livelihoods towards tourism employment. [ABSTRACT FROM PUBLISHER]

This 210-day study compared variation in water quality and fish growth for channel catfish (Ictalurus punctatus; 47 g/fish) stocked in earthen ponds (1.5 fish/m2, 14,820/ha) and in a biofloc technology (BFT) production system with high-density polyethylene-lined rectangular tanks (12.6 fish/m2, 126,000/ha). Feed input and culture environment affected water-quality dynamics. In ponds, phytoplankton uptake predominated and little nitrification occurred, whereas in the BFT system phytoplankton uptake and nitrification maintained low ammonia-nitrogen concentrations. Size classes of fish were skewed toward the larger market sizes in ponds and toward smaller market sizes in the BFT system. Mean final fish weight was 630 g/fish in ponds and 542 g/fish in the BFT system. Despite these differences, fish yield was higher in the BFT system (7.7 kg/m3v. 1.5 kg/m3) because of the greater initial stocking rate. [ABSTRACT FROM PUBLISHER]

Stock assessments of quota or effort managed fisheries in which the duration of the fishing season is 12 months are invariably delivered well into the subsequent fishing season. As a result, quotas are frequently based on year-old data. This delay is often unavoidable because it may take months to collect, collate and analyse data necessary to assess fishery performance. The South Australian fisheries for blacklip (Haliotis rubraLeach, 1814) and greenlip abalone (H. laevigataDonovan, 1808) have addressed this issue by using provisional data on current stock status to inform application of the harvest strategy decision rules that set the quota for the next year. The primary index of relative abundance for these fisheries is catch per unit effort (CPUE). Our study uses 25 years (1988–2012) of CPUE data to quantify the differences between the provisional and complete-season CPUE estimates at the spatial scales used to assess the fisheries. We demonstrate that, in most cases, there was a strong relationship between the provisional and complete-season CPUE estimates for both species, with little evidence of bias. As the provisional CPUE estimates were a reliable and accurate predictor of the complete-season CPUE estimates, this provides a high degree of confidence in using provisional CPUE estimates to set quotas, thereby overcoming the difficulty of basing decisions on aged data. These findings are likely to be applicable to other fisheries, particularly those where much of the annual catch is obtained (or effort expended) in a short time period at the commencement of the fishing season. [ABSTRACT FROM PUBLISHER]

The present on-farm study assessed the effect of different stocking densities on growth, production, and financial benefits of African sharptooth catfish (Clarias gariepinus) in earthen ponds for 180 days. Low stocking density (LSD), medium stocking density (MSD), and high stocking density (HSD) of 3, 6, and 9 fish m−2, respectively, were tested.C. gariepinusstocked at LSD and MSD showed significantly higher weight gain, specific growth rate, and final mean weight than those cultured at HSD (P < .05). There was a significant linear relationship between the stocking density and the yields and financial variables (P < .05). Net fish yields were significantly higher forC. gariepinusreared at HSD and MSD than those stocked at LSD (P < .05). Similarly,C. gariepinusraised at MSD and HSD generated significantly more profit than those cultured at LSD (P < .05). Results demonstrated that farmers can achieve high net yield and financial benefits by stockingC. gariepinusat HSD of 9 fish m−2. [ABSTRACT FROM PUBLISHER]

We used an experimental manipulation to determine the impact of stocking 178 mm channel catfishIctalurus punctatusin six impoundments. The study design consisted of equal numbers (two) of control, ceased-stock, and stocked treatments that were sampled one year before and two years after stocking. Relative abundance, growth, size structure, and average weight significantly changed over time based on samples collected with hoop nets. Catch rates decreased at both ceased-stock lakes and increased for one stocked lake, while growth rates changed for at least one ceased-stock and stocked lake. The average weight of channel catfish in the ceased-stock treatment increased by 6% and 25%, whereas weight decreased by 28% and 78% in both stocked lakes. The variability in observed responses between lakes in both ceased-stock and stocked treatments indicates that a one-size-fits-all stocking agenda is impractical, suggesting lake specific and density-dependent mechanisms affect channel catfish population dynamics. [ABSTRACT FROM AUTHOR]

The effect of photoperiod (24L:00D, 12L:12D, and 00L:24D) and temperature (22 ± 1°C and 28 ± 1°C) on performance ofClarias gariepinuslarvae was tested. Larvae weighing 3.2 ± 0.24 mg were cultured in aquaria at a stocking density of 20 fish L−1and fed twice a day on catfish starter diet (40% CP) at 10 % BW day−1. Highest mean weight gain (31.00 mg), SGR (7.56% day−1), and survival (83%) were achieved at photoperiod and temperature combination of 00L:24D and 28 ± 1°C. Percent survival of larvae differed significantly (p < .05) among treatments with optimal survival of (83%) in treatment combination of 28 ± 1°C and 00L:24D, while lowest survival (40%) in treatment combination of 22 ± 1°C and 24L:00D. [ABSTRACT FROM PUBLISHER]

Phosphorus fertilization is employed in some reservoirs to increase fish production. To clarify whether silver carp regulate phosphorus (P) concentration or if fertilizing leads to phytoplankton blooms, a 6-week experiment was conducted with 18 enclosures in Nanwan Reservoir, central China. Treatments were three levels of P concentration (low: 45 μg/L; medium: 90 μg/L; high: 180 μg/L) with or without silver carp stocking (10 g/m3). The effect of silver carp stocking on phytoplankton community changed with P fertilization in the water column. No significant fish effect was observed on total phytoplankton biomass at the low P level, while the chlorophyllaconcentration, total phytoplankton biomass, and biomass of phytoplankton > 30 μm were enhanced significantly by silver carp at the medium P level. In addition, at the medium P level, the biomass of Bacillariophyta was significantly greater, whereas the biomass of Chlorophyta was significantly lower in the enclosures with silver carp stocking. Potentially, silver carp enhanced the total phytoplankton biomass by nutrient recycling. Zooplankton had a weak grazing efficiency and had limited effects on control of phytoplankton biomass at the three P levels. The 6-week experiment confirmed that P fertilization could consistently cause greater fish productivity with phytoplankton biomass increasing at the same time. We therefore propose a mechanism for the observed relationship between silver carp stocking and phytoplankton. Under the condition of ambient fish density (10 g/m3), silver carp could not control phytoplankton biomass with phosphorus fertilization; instead, the fish may have promoted phytoplankton growth via nutrient recycling. Silver carp seem to have only a weak effect on the phytoplankton community without P fertilization. Therefore, from the viewpoint of phytoplankton regulation, P fertilization should be considered as a cautious operation for water protection and reasonable fish enhancement. [ABSTRACT FROM AUTHOR]

A pterosaur wing phalange from the Kimmeridgian of Eathie (Ross and Cromarty) is identified as the first pterosaur to have been collected in Scotland. The specimen was acquired by the British Museum (Natural History) in 1888, but an old collector's label gives the date of collection as 1850. The handwriting matches that of Charles W. Peach (1800-1886), who later became better known for his fossil fish and plant collections, which still exist in the Natural History Museum, London, and other museums. Peach collected this pterosaur specimen during his first year of working in Scotland, and it was probably one of his earliest finds of north of the border. Pterosaur remains are exceptionally rare in Scotland and otherwise unknown from this particular site, so this newly recognised specimen is a significant addition to the Scottish fossil record. It is also among the earliest UK pterosaur finds, post-dating Mary Anning's discovery of Dimorphodon by just over two decades. [ABSTRACT FROM AUTHOR]

Inappropriately high stocking density can lead to chronic stress that causes many problems in fish culture. We examined the influence of stocking density on growth performance and a number of key serum parameters of Atlantic salmon (Salmo salar) to investigate stress-induced changes. Salmon were reared at low-density (~7.57–15.71 kg/m3, initial to final density), medium-density (~15.12–31.11 kg/m3), and high-density (~30.18–61.34 kg/m3) stocking levels for 10 weeks. The results showed that stocking density had significant influence on the growth rate, specific growth rate, and feed conversion ratio (p < 0.05) but not on condition factor and mortality. All examined seven serum parameters showed significant change in the first few weeks. Five parameters increased in all three stocking densities, while the serum superoxide dismutase (SOD) and alkaline phosphatase (ALP) activities decreased. At the end of the experiment, the immunoglobulin M level and SOD activity were lowest in the high-density group (p < 0.05), while the cortisol level, ALP activity, and maleic dialdehyde content were significantly higher than in the other two groups (p < 0.05). The acid phosphatase (ACP) and lysozyme activities were not affected by stocking density. These results indicate that high stocking density could affect the growth of Atlantic salmon and the selected serum parameters, except for lysozyme and ACP, could be used as good indicators for chronic stress caused by stocking densities that are too high. [ABSTRACT FROM AUTHOR]

An experiment was conducted to ascertain the initial rearing period required forHorabagrus brachysomalarvae before releasing them into the nursery tank for fingerling production. Hatchlings were reared for 7, 14, or 21 days in larval rearing tanks before stocking to nursery tanks. The 7-day-old larvae were significantly smaller at the end of the 2-week nursery rearing, but over the course of nursing, the 7-day-old larvae caught up to the 14- and 21-day larvae. The specific growth rate (SGR) of 7-day larvae was highest among the three treatments. However, mortality of 7-day larvae was the highest among the groups. Hence, it appears important to rear the larvae at least 2 weeks before stocking for fingerling production so as to increase survival rate. [ABSTRACT FROM AUTHOR]

SardineSardinops sagaxdistributed off the west and south coasts of South Africa have traditionally been assumed to comprise a single well-mixed stock for assessment and management purposes. New research, however, lends weight to the possibility of two stocks in this region. A precautionary management approach thus needs to consider the impact of management decisions on the hypothesised two individual stocks as well as on the resource as a whole. As a first step in this process, Bayesian assessments of South African sardine are presented, which compare results for the traditional single-stock hypothesis with those that follow from a new two-mixing-stock hypothesis. Recruits from the west stock are assumed to move to and remain part of the south stock in annual pulses of varying size. This movement is estimated to be appreciable, and to take place from a substantially more productive west stock to the south stock. This immigration makes a greater contribution to the south-stock biomass than do years of above-average south-stock recruitment. Importantly, this two-mixing-stock hypothesis is shown to be consistent with the data available. Further alternative sardine stock-structure hypotheses suggested by the most recent data are discussed. [ABSTRACT FROM AUTHOR]

A factorial design with three levels of dissolved oxygen (DO)—low 1.0–1.5 mg/l (LDO), medium 2.5–3.0 mg/l (MDO), and normal 6.0–6.5 mg/l (NDO)—and two stocking densities—0.2 g/l (SD1) and 0.4 g/l (SD2)—tested the interaction between oxygen and stocking density on juvenile tilapia performance. After the feeding trial, fish were intraperitoneally injected by pathogenic bacteria,Aeromonas hydrophila, and fish mortality was observed for 10 days post challenge. Highest growth was observed in the NDO-SD1 group. Reduction in DO concentration from 6.5 to 3.0 or 1.5 mg/L caused a reduction in fish growth and feed intake, which increased significantly by increasing fish density. Crude protein and total lipid in whole-fish body decreased significantly at LDO, while total lipid content decreased also at high SD. Glucose, activities of aspartate amninotransferase and alanine aminotransferase, creatinine, and uric acid in fish sera increased significantly, while total protein and total lipid decreased significantly at LDO and/or high density. Lowest fish immunity was observed in the LDO-SD2 group, suggesting that stress was maximized under LDO conditions and/or at high density. [ABSTRACT FROM AUTHOR]

As a result of the concern and debate about the impacts of intensive aquaculture development on biodiversity, semi-intensive aquaculture is being considered as an alternative. Although the biophysical impacts of aquaculture on biodiversity have been examined, there is only limited understanding of the social and economic impacts of aquaculture on biodiversity, and especially the impacts of the shift from intensive to semi-intensive systems. The purposes of this article are twofold: (1) to identify and discuss the social and economic impacts of aquaculture on biodiversity, and (2) to examine the impacts while moving from intensive to semi-intensive systems. After discussing the findings of our study, we provide some recommendations as to how to minimize social and economic impacts of aquaculture on biodiversity by moving to a lower intensity aquaculture system. The integrated agriculture-aquaculture farming systems, stakeholder involvement in management, and well defined basic rights are aquaculture systems that contribute to conservation of biodiversity. [ABSTRACT FROM PUBLISHER]

The escape of cultured fish from a marine aquaculture facility is a type of biological invasion that may lead to a variety of potential ecological and economic effects on native fish. This article develops a general invasive species impact model to capture explicitly both the ecological and economic effects of invasive species, especially escaped farmed fish, on native populations and harvests. First, the possible effects of escaped farmed fish on the growth and stock size of a native fish are examined. Next, a bioeconomic model to analyze changes in yield, benefit distribution, and overall profitability is constructed. Different harvesting scenarios, such as commercial, recreational, and joint commercial and recreational fishing are explored. The model is illustrated by a case study of the interaction between native and farmed Atlantic salmon in Norway. The results suggest that both the harvest and profitability of a native fish stock may decline after an invasion, but the total profits from the harvest of both native and farmed stocks may increase or decrease, depending on the strength of the ecological and economic parameters. [ABSTRACT FROM PUBLISHER]

Many marine fish stocks are overexploited and considerable overcapacity exists in fishing fleets worldwide. One of the reasons for the imbalance between resource availability and fishing capacity is technological development, which continuously increases the efficiency of the vessels--a mechanism referred to as "technological creep." We review how the introduction of new and more efficient electronic equipment, gear design, engines, deck equipment, and catch-handling procedures influences the capture efficiency (catchability) of commercial fishing vessels. On average, we estimate that catchability increases by 3.2% per year due to technological developments, an increase often ignored in fisheries management. The documentation and quantification of technological creep improves the basis for successfully integrating the effects of technological development (and catchability changes) in fisheries management regulations and policies. Ways of counteracting the undesired effects of technological creep are discussed as are the potential management benefits from improved fishing technology. Specific suggestions are given on the selection, application, and tuning of fisheries management tools that can be used to improve the balance between harvesting capacity and resource availability. [ABSTRACT FROM AUTHOR]

Rising costs of feed ingredients in recent years have resulted in record increases in catfish feed prices. Since understocked channel catfish (Ictalurus punctatus) do not reach market size until the second year of production, static one-year economic models and analyses may not be adequate. A previous mixed-integer profit-maximizing model was extended to include a second year to evaluate the effects of varying feeding frequencies on farm management decisions, particularly on adjustments in the second year. Production options considered included frequency of feeding (every day, every other day, and every third day), multiple-batch production from four different fingerling sizes, and single-batch production from three different stocker sizes. Every day feeding was identified as the profit-maximizing feeding strategy on farms using multiple-batch production but unfavorable market prices, high feed prices, and operating capital constraints reduced feeding frequencies. Every day feeding remained the optimal strategy for farms in single-batch foodfish production. Market and capital constraints reduced the scale of farms operating in single-batch foodfish production, but did not change the optimal every day feeding strategy. Farms maximized profits by transitioning from multiple batch to single batch over the two-year period. [ABSTRACT FROM AUTHOR]

Effects of stocking density on the growth, production, and economics of all-male tilapia (Oreochromis niloticus) were investigated in a rain-fed rice-fish ecosystem for a period of 120 days. Fish were stocked at the rate of 4000, 5000, and 6000 ha−1in treatments T1, T2, and T3, respectively. Water quality was suitable for fish culture. Significantly higher growth was observed in T1as compared to other treatments. SGR ranged from 1.26 to 1.51. Survival varied between 79% and 88% with treatment T1producing the highest survival. The highest benefit:cost ratio was obtained in T2followed by T1and T3. The best fish production (457.21 kg ha−1) and economic return for the culture period was obtained at 5000 fish ha−1. [ABSTRACT FROM PUBLISHER]

This article—based on ethnographic research on fish stocking and discourses surrounding authenticity, aesthetics, and taste of wild fish in Japan—examines the cultural production of the “wilderness.” While Japan's seafood culture has long historical roots, this fetishism of wild fish is a product of the recent advancement of fisheries technology, namely aquaculture and fish stocking. The expansion of aquaculture has shaped not only the notion of the “cultivated” but also that of the “wild.” Simultaneously, the development of fish stocking—the national project to enhance wild fish stocks by releasing hatchery-bred juveniles into the ocean—has also contributed to the reimagining of the authenticity of “wild” fish while complicating it. By looking at flounder, one of the most popular species for fish stocking, this article reveals that tasting “wilderness” is a multisensory experience that reflects not only gustatory but also visual dimensions. [ABSTRACT FROM PUBLISHER]

The effects of release habitat on the effectiveness of stocking were evaluated in Miyako Bay, Iwate, Japan. Hatchery-reared black rockfish juveniles were released at four different stations characterized by different habitat conditions from 2002–2007, and a survey was conducted of landed fish at Miyako Fish Market. Growth rate and feeding condition of wild and released juveniles sampled from two known wild nursery areas (Stn. 1 and Stn. 2) were also examined to elucidate the conditions that form optimal habitat. Comparisons of growth and feeding condition of juveniles between Stn. 1 and Stn. 2 indicated that Stn. 1, with its brackish waters, seagrass beds, abundant mysids, and large gammarids, supported better growth and survival of released fish, which in turn led to a higher market return rate. The highest market return rate was estimated as 8.3% (for 45-mm total length juveniles released at Stn. 1 in 2007), corresponding to a maximum economic return rate (value of recaptured fish divided by hatchery and release costs) of 1.32. [ABSTRACT FROM PUBLISHER]

In this study, an integrative review of the potential for stock enhancement is conducted to support desirable management outcomes in marine recreational fisheries, focusing on the Florida, USA, red drum fishery as a case study. Here, stock enhancement is implicitly seen as a way of simultaneously achieving both ecological objectives of sustained wild fish populations and socioeconomic objectives of high fishing effort and/or catch rates. However, the review suggests that a fundamental tradeoff remains between these objectives in the short-term because stocking of hatchery fish is likely to result in at least partial displacement of wild fish through biological interactions as well as increased fishing pressure. Contrary to the perception of enhancement as a “quick fix,” successful use of the approach in the marine recreational fishery is likely to require sophisticated stock management and some adaptation in governance. In developing the enhancement, it will be necessary to address uncertainty in key attributes, specifically dynamics of recruitment, angler-effort responses, and stakeholder involvement. This may be achieved by combining quantitative modeling, monitoring, and stocking experiments in an active adaptive management framework to consider enhancement in the context of alternative management strategies. It is suggested that any interim enhancement should minimize ecological risk per socioeconomic benefit by stocking larger fish in areas where high fishing mortality limits abundance of wild fish. These conclusions are largely generalizable to other recreational enhancements, and this work serves as a model of rarely published a priori enhancement evaluation. [ABSTRACT FROM PUBLISHER]

Aquaculture-based enhancement of marine fisheries includes sea ranching, stock enhancement, and restocking. A rapidly evolving context and maturing science base have effectively put these approaches into the fisheries management toolbox. Among the contextual factors are (1) a rapid expansion of captive breeding and domestication to new marine species, (2) fisheries governance systems that address the common dilemma, and (3) global environmental change impacts on coastal fisheries that increasingly call for active approaches to maintaining or increasing fisheries yields and ecosystem services. The science base of marine restocking, stock enhancement, and sea ranching continues to advance rapidly and has now reached a point where it is becoming possible to assess the likely contribution of such approaches to fisheries management goals prior to major investments being undertaken and to design enhancement programs effectively and responsibly where good potential is judged to exist. This signifies an important transition of marine fisheries enhancement from an exploratory, research-oriented endeavor to a tool in the fisheries management tool box. [ABSTRACT FROM PUBLISHER]

The potential for restocking with hatchery organisms as a tool to rebuild depleted populations of blacklip abalone(Haliotis rubra)was investigated through replicated, control-impact studies in New South Wales, Australia. Long-term survival (>2 years) of hatchery-reared and released abalone, their impact on wild abalone abundance, and the effect of diffuse versus concentrated release was investigated on natural reefs. Long-term survival of released hatchery abalone varied between releases but averaged about that expected for wild abalone. There was no significant effect of released juveniles on the persistence or recruitment of wild abalone. Significantly greater numbers of all (released and wild) abalone persisted at release locations through time, while the total number of wild abalone increased significantly through time at release and control locations. There was no significant difference in long-term survival of abalone released in clusters of high density (2–4%) or in a diffuse or concentrated array (0–9%). These results show that restocking can supplement natural rebuilding processes of depleted wild abalone populations in New South Wales, Australia. [ABSTRACT FROM PUBLISHER]

This study presents a bioeconomic evaluation of the effect of stock enhancement on biomass, net present value, profitability, and gross value of product of the Australian greenlip abalone(Haliotis laevigata)fishery. Enhancement targets were defined as a function of natural recruitment(Nr)and compared with current harvest strategies. The model was conditioned on a Western Australian fishery, then applied to greenlip stocks throughout Australia. Two levels of releases (50%Nrand 100%Nr) at varying fishing mortality(F), size at harvest, and size at release were evaluated in detail. Model validation was also undertaken by comparing the model-derived spawning biomass(SSb)with an alternative estimate(SSbf)obtained using in-water surveys and a different growth model. Economic profitability and increased spawning biomass were achieved for most stock enhancement scenarios, and optimal profitability occurred with a 10–20% decrease inFfrom current levels, a 10% decrease in minimum legal length, and an annual enhancement ofNrjuveniles to match natural recruitment. More radical scenarios, such as an annual release of 150%Nrcombined with a 30% decrease in size at harvest resulted in greater profitability (+175%) but presented a higher risk of wild stocks being replaced with hatchery genotypes. Sensitivity analysis revealed that mortality, size at release, and harvest price were the critical parameters, while costs of production and fishing were less important. At the national scale, an enhancement scenario involving an annual release of 6.1 million 4-cm juveniles (∼age 2) resulted in a 60% increase in gross value of product ($25 to $40 million), a 120% increase in profitability ($12 to $26 million), and net present value ($190 to $420 million; 6% discount), and a 25% increase inSSb. [ABSTRACT FROM PUBLISHER]