Hasil untuk "Aquaculture. Fisheries. Angling"

T. Chopin, A. Tacon

Abstract The FAO recently published its biennial State of World Fisheries and Aquaculture up to 2018. The FAO continues to treat the seaweed aquaculture sector as a different category, with separate tables and comments in different sections. As this could lead to a distorted view of total world aquaculture, the statistical information provided by FAO was revisited and data regarding the seaweed aquaculture sector were integrated with data of the other sectors of the world aquaculture production, to reach different conclusions: (1) aquaculture represents 54.1% of total world fisheries and aquaculture production; (2) marine and coastal aquaculture represents 55.2% of total world aquaculture production; (3) seaweeds represent 51.3% of total production of marine and coastal aquaculture; (4) 99.5% of seaweed mariculture production is concentrated in Asia; (5) 8 seaweed genera provide 96.8% of world seaweed mariculture production; (6) 2 seaweed genera are the most produced organisms in mariculture in the world; (7) the value of the seaweed aquaculture sector could be much larger, especially if a monetary value was attributed to the ecosystem services provided by seaweeds; and (8) total extractive aquaculture is slightly larger (50.6%) than total fed aquaculture (49.4%).

Lin He, Bo Jiang, Xiafei Zheng et al.

Dynamic Energy Budget (DEB) theory seeks to quantify the energetic framework of individual organisms through a dynamic model that encompasses food uptake and its subsequent utilization in metabolic processes. This paper aims to extend the existing DEB model for Tegillarca granosa in pond culture. The model is influenced by water temperature and food density, which serve as key forcing variables throughout larval development. We calculated DEB parameter values for larvae through laboratory experiments specifically designed to gather datasets on ingestion and growth under varying phytoplankton densities and temperatures. Sensitivity analysis indicated that Arrhenius temperature (TA) exerted the most significant impact on growth, with a 10 % increase in TA resulting in an 11.6 % increase in dry tissue weight. Insufficient energy allocated to storage during January and February hindered the growth of T. granosa, leading to reduced dry tissue weight, structural damage, and decreased survival rates during winter. This study provides theoretical insights into assessing the carrying capacity and implementing scientifically informed aquaculture management practices for T. granosa in pond systems.

Mahmoud M. Abdel-Hady, Ahmed F. El-karashily, Ahmed M. Salem et al.

This study assessed the sustainability of capture-based aquaculture (CBA) practices in Egypt, identified challenges, and proposed solutions to enhance sustainability. It relied on published data and studies, revealing that these practices are globally widespread for cultivating a diverse range of marine and freshwater species based on wild seed collection. The assessment showed that these practices in Egypt cultivate a variety of fish species. In 2021, they contributed to approximately 34% of the total aquaculture production, amounting to an estimated value of USD 1.476 billion, representing about 57% of the total value of the aquaculture sector. Additionally, these practices provided around 106,022 full-time jobs. Official fishery statistics have not indicated any negative impact of CBA on fish stocks over the past 30 years. Measures aimed at enhancing the sustainability of these practices included granting licenses for the collection of wild seeds for specific species under specific regulations. Facilitating licensing procedures for hatcheries, providing incentives, and promoting farmers’ preferences for hatchery seed were also part of these measures. Furthermore, these actions include facilitating access to financing under favorable conditions, selective breeding, training hatchery workers in best management practices, implementing biosecurity measures, and establishing an accurate statistical system. The implementation of the proposed plan to transition from capture-based aquaculture to hatchery-based aquaculture will contribute to achieving sustainability for both aquaculture and fisheries.

William W. L. Cheung, Daniel Pauly, U. Sumaila

Marine fisheries are crucial to the economy, livelihood, food security and culture of coastal nations and communities, significantly contributing to the United Nations Sustainable Development Goals. A decade ago, T. J. Pitcher and W. W. L. Cheung highlighted the dichotomy in the perception of fisheries' status, concluding that long‐term sustainability and benefits to people were threatened by overexploitation, climate change, pollution, habitat change and other human stressors. They advocated for a fundamental shift towards ecosystem‐based management, better enforcement of existing regulations and more inclusive and equitable management practices. In this paper, we provide an updated review of the status of global fisheries, reflecting on policy actions, key assessments and research findings over the past decade. While there is a growing recognition of the need for sustainable fisheries management and ocean protection, the overall status of fisheries has not improved. Despite progress in international and national policies addressing direct and indirect drivers such as climate change and harmful practices, these trends have not been reversed. Many challenges identified by Pitcher and Cheung and others persist. Additionally, new and emerging issues such as deep‐sea mining, plastic pollution, unhealthy aquaculture development, increasing social inequity and the rapidly increasing push for the acceleration of the blue economy exacerbate the complexity of achieving fisheries and other ocean management goals. Debating whether there is more hope or despair in global fisheries has become irrelevant. Pathways to ‘bend the curve’ for fisheries are clear, and effective actions are now urgently needed to achieve desirable and sustainable fisheries.

Nickolis Black, Thomas M. Banks, Tomer Ventura

In the wake of global population increases and stagnating capture fishery production, there exists a requirement for novel biotechnologies to increase aquaculture productivity to offset demand. Through recognition of limitations imposed by aquaculture—increased incidence of disease, stress, cannibalism, and mortality in captivity—researchers continue to investigate RNA interference (RNAi) and clustered regularly interspaced short palindromic repeat (CRISPR) technologies for their potential to alleviate these at a genetic level. In decapods, with the exception of generating desirable all‐male monosex populations in Macrobrachium rosenbergii, RNAi and CRISPR technologies have yet to provide a significant commercial use case. This literature review provides a comprehensive examination of RNAi and CRISPR in decapods, along with popular delivery methods (injection/microinjection; electroporation; receptor‐mediated ovary transduction of cargo [ReMOT]; and nanoparticles). It identifies a number of limitations including scalability bottlenecks imposed by RNAi delivery methods, and deferred gene editing progress as a result of CRISPR's infancy. Finally, it recognises gene editing induced gene silencing (GEiGS®) as a novel method for silencing gene expression, and suggests an interim examination of transgenerational gene silencing (TGS) (‘parental RNAi’) in decapods to enhance aquaculture productivity.

Kai MA, Guangxiang TONG, Lanlan ZHANG et al.

The genus Thymallus, belonging to the Salmoniformes, Salmonidae and Thymallinae, is distributed in three main areas in China, namely, the Irtysh River Basin, the Heilongjiang River Basin and the Yalu River Basin. Research has shown that the diversity of extant Thymallus in China is much higher than that in the vast European and North American regions, but the taxonomic results of some species are still controversial. Among them, those whose taxonomic status has been clarified and whose nomenclature is not controversial are T. arcticus, T. grubii and T. tugarinae, and the one that is still controversial is T. yaluensis. Named by Mori in 1928, T. yaluensis is mainly distributed in the Yalu River Basin and is geographically isolated from the T. arcticus, T. grubii and T. tugarinae. In 2007, a study on the comparison of countable traits of Thymallus found that the countable traits of the T. yaluensis were in the middle between the T. grubii and T. tugarinae, and the validity of the taxonomic status of T. yaluensis has been formally questioned ever since; in 2008, a study using mitochondrial DNA control region sequences to study the evolutionary relationships of fishes in the genus Thymallus pointed out that the T. yaluensis is synonymous with the T. grubii. In 2016, researchers used mitochondrial genome data to confirm once again that there was no difference between the T. yaluensis and the T. grubii. However, this conclusion does not seem to be accepted by the academic community, and in recent years, there are still some scholars who regard the T. yaluensis as an independent species. Morphological methods are the most commonly used methods in species identification, which can be categorized into traditional morphological method and framework measurement method. The traditional morphological method mainly analyzes the horizontal and vertical traits of the fish body, and it is mostly limited to the head and tail traits, which can't measure the whole surface of the fish body comprehensively. The framework measurement method, however, is based on a certain number of anatomical coordinate points and measures the entire fish body in multiple directions, which can provide a more comprehensive response to the morphological differences of the fish body. So far, the studies on the interspecific differences of Thymallus in China have mostly focused on the molecular biology level, while the morphological differences have been less studied, only in T. grubii and T. tugarinae. The rapid development of molecular marking technology provides an important auxiliary means for species classification, but the apparent morphological differences are still recognized as the most intuitive basis for species classification. In order to clarify the morphological differences of Thymallus in China, this study comprehensively used traditional morphological methods and framework measurement method, and took the T. grubii, T. arcticus, T. yaluensis and T. tugarinae as the research objects, Statistical analysis was conducted on their 10 segmentation characteristics and 32 standardized metric features. The results showed that: (1) there was no significant difference (P > 0.05) between all the subsection characteristics of T. yaluensis and T. grubii, and there were significant differences (P < 0.05) in more than five segmentation characteristics between T. grubii, T. arcticus and T. tugarinae. (2) The coefficient of variation analysis showed that except for caudal peduncle length/body length, the differences in morphological characters between T. yaluensis and T. grubii were at the level of differences between geographic populations within species. (3) The principal component analysis screened out eight principal components with eigenvalues greater than 1, and the cumulative contribution rate reached 81.170%, among which the first and second principal components with the highest contribution rate mainly explained the differences in trunk and head between Thymallus, respectively. The construction of scatter plots of the first and second principal components revealed that the individual crossover between T. yaluensis and T. grubii had a high degree and could not be distinguished individually, while T. tugarinae and T. grubii show a lower level of overlap and partial distinction. Only T. arcticus can be distinctly separated. (3) Discriminative analysis was used to screen out 14 standardized measurement features to establish the Fisher linear discriminant function, and the discriminative rate of individuals being correctly assigned to their respective groups was as high as 97.30%. (4) Cluster analysis showed that compared with T. grubii, T. yaluensis had the highest degree of similarity with it, followed by T. tugarinae, and T. arcticus had the lowest degree of similarity with T. grubii. The comprehensive analysis showed that: (1) T. yaluensis should not be designated as a valid species and its scientific name should be revised to T. grubii. (2) Morphological differences among T. grubii, T. arcticus and T. tugarinae are mainly reflected in their segmentation characteristics and the measurement characteristics of trunk and head. The results of this study will provide a reference for the study of species classification and evolutionary relationships of the genus Thymallus.

Niklas Warwas, Emma L. Berdan, Xintian Xie et al.

A nutritional bottleneck in salmonid aquaculture is the procurement of marine-derived compounds, such as essential amino and fatty acids, including omega-3 fatty acids, lysine, and methionine. Therefore, insects containing these compounds are highly promising as feed ingredients. The present study evaluates larvae of a “marine” insect (Coelopa frigida, the bristly-legged seaweed fly larvae, SWFL) reared on brown algae side streams as a feed ingredient for rainbow trout (Oncorhynchus mykiss). SWFL contained, on a dry matter basis, 60% crude protein (CP), 3.5% lysine, and 1.5% methionine, as well as 17% lipids, including 4% eicosapentaenoic acid and docosahexaenoic acid. Four isoenergetic (ca. 23 MJ kg−1 gross energy) and isoproteic (ca. 45% CP) feeds were evaluated in a 10-week feeding trial. The diets included a control containing 25% fish meal, a commercial reference, and two diets substituting 40% fish meal with either SWFL or partially defatted black soldier fly larvae (BSFL) meal (Hermetia illucens). SWFL-fed fish displayed higher specific growth rates (SGR) compared to BSFL-fed fish and similar SGR compared to control and reference diet-fed fish. Feed intake in SWFL-fed fish was higher than for the control and BSFL diets and similar to the reference diet. The feed conversion ratio of fish fed the BSFL and SWFL diets was higher compared to the control, suggesting lower bioavailability of both insect meals compared to fish meals. No difference in intestinal health parameters was noted between the insect diets and the control diet, indicating good intestinal health across all treatments. However, changes in electrogenic intestinal transport were observed between the SWFL and BSFL diets, illustrating the heterogeneous effect of different insect products. Overall, SWFL meal is a promising alternative marine feed ingredient, compatible with circular production systems, as it can be efficiently cultivated using marine side streams.

Zichu Yuan, Jiayan Niu, Kangxiang Qin et al.

Salinity affects the growth and development of crustaceans by affecting their physiological functions such as respiration, metabolism, osmotic regulation and immune defense. Gill is the most important organ of osmotic regulation. The adaptation of Scylla paramamosain to low salt is a process of oxygen consumption and energy consumption, and the mitochondria in the cells are considered to be the synthesis site of energy. Therefore, in this study, GC-MS technology was used to conduct non-targeted metabolomics studies on the posterior gill mitochondria of S. paramamosain under acute hyposaline stress, revealing the key role of mitochondria in gill response to acute low salinity stress. We identified 196 metabolites, 21 of which were differentially expressed. Differential metabolite KEGG enrichment analysis identified 16 metabolic pathways. The results of this study suggest that mitochondria may maintain osmotic homeostasis by increasing the utilization of monosaccharides, and decreasing the synthesis of amino acids in crabs under acute low salt stress when they are in a state of oxygen and energy depletion. In addition, carbohydrates and organic acid metabolites may also play an important role. For the first time, we analyzed the metabolic mechanism of posterior gill mitochondria in response to acute low salt, aiming to provide effective technical support and theoretical reference for the cultivation of S. paramamosain.

K. Fiorella, H. Okronipa, Katherine Baker et al.

Aquaculture is increasing the global supply of foods, and holds tremendous potential to address malnutrition and diet-related diseases. The species selected and feeds used affects the nutrients available from aquaculture. Progress in the development of novel and sustainable aquaculture feeds to reduce reliance on wild fisheries, feed fortification to increase nutrient content, and expansion of the diversity of aquatic species produced are key areas for continued research and development. Ultimately, the degree to which aquaculture will contribute to nutrition depends largely on who can access the fish produced, which will be shaped by production technology as well as trade and price dynamics. Finally, the contribution of aquaculture expansion to improving nutrition will be bounded by aquaculture's environmental sustainability.

Antar Sarkar, Saifuddin Rana, Pranta Bhowmik et al.

Suckermouth armoured catfish of the genus Pterygoplichthys (Siluriformes: Loricariidae) are significant threats to aquatic biodiversity, ecosystems, habitats, and fishery production in different countries. Their unique characteristics and adaptive features help their successful invasion. These fish harm fish habitats, compete for food and space, prey on fish eggs, and displace the native fish populations. They erode river banks, alter benthic ecology, make holes in the river bank, and remove aquatic plants. Elimination, control, and intrusion prevention are possible management strategies. Utilising them as food and preparing value-added products and byproducts using them are viable ways to reduce their number. Management is challenging, owing to their tolerance and excellent adaptability. With severe dangers to Bangladesh's fisheries industry and aquatic environment, suckermouth armoured catfish have invaded natural waterbodies and aquaculture ponds. There is a lack of accurate information on invasion status, types of invading species, and potential dangers of invasion to create a management framework in Bangladesh. Therefore, this review introduces the key characteristics, habitats, invasion impacts, and management and utilisation aspects of suckermouth armoured catfish in different countries. The review may help in understanding how they affect native fish, aquatic organisms, habitats, and the aquatic environment globally. Finally, what kind of threats they may pose and how they can be managed sustainably in Bangladesh.

Sahar F. Mehanna et al.

Egyptian fisheries including aquaculture, play a vital role in the national economy through its contribution to employment and income generation, foreign exchange earnings, and providing food and nutritional security to the people. All studies dealing with stock assessment and fisheries management in Egypt confirmed the over-exploitation situation for almost all commercial stocks which led to a serious decline in fish production from marine and inland fisheries resources. Egyptian lakes especially

M. Bhendarkar, B. Gaikwad, A. Bhalerao et al.

The COVID-19 pandemic-induced lockdown has indisputably affected the aquaculture industry across the globe. India imposed a nationwide lockdown to contain the outbreak of COVID-19 that disrupted normalcy and economic activities. The fisheries sector was also highly affected. Hence, a study was conducted from July to December 2020 to understand the stakeholders’ perception of the impact of COVID-19 lockdown, wherein 517 stakeholders participated (online) in the first stage. The policy reforms suggested by the stakeholders were referred to the fisheries experts in the second stage for prioritization towards implementation. Data analysis depicted that a majority (81%) of the stakeholders were aware of COVID-19 lockdown impacts on their businesses. Due to this unprecedented lockdown, labour availability was hampered, transport facilities were fully halted and access to inputs like seed, feed, and advisory were largely affected. Importantly, all stakeholders unanimously adduced to the uncertainty over the future of the fisheries sector. Moreover, fishery experts feel that enabling policies for the promotion of awareness, appropriate training, and transparency in the implementation of schemes, credit facilities, and price regulation can have a massive positive impact. Furthermore, the study also recommends utilizing the potential of e-resources (ICTs and IoT) to digitize the business networking of fishery sector stakeholders.

Cuiqin MO, Kai HUANG, Xinsheng CAO et al.

Procambarus clarkii Girard is an economically important cultured shrimp in China, and lipids are an important component of its raw feed materials. Studies have shown that adequate lipid content in feed can promote the health of aquatic animals, improve the utilization efficiency of feed protein, save protein, reduce feed costs, and reduce nitrogen emissions. Insufficient lipid content in feed leads to metabolic disorders in breeding animals, reduces the utilization rate of feed protein, and is accompanied by a deficiency of fat-soluble vitamins and essential fatty acids. However, a high fat content inhibits feeding and growth and leads to excessive fat deposition in the fish body, which decreases disease resistance and is not conducive to feed processing and storage. At present, studies on the dietary lipid content of P. clarkii have mainly focused on growth performance, biochemical indices, and conventional nutritional components of muscle; however, studies on muscle quality, amino acid composition, and content have not yet been reported. This study investigated the growth performance, muscle texture indices, nutritional components, and food flavor of P. clarkii by determining the effect of dietary lipid content on the growth performance and muscle quality of juveniles. The aim of this study was to provide a reference for the development of compound feed for juvenile P. clarkii and to provide a theoretical and scientific basis for rationally evaluating the effects of fat on the muscle quality of the species.Five experimental diets with lipid levels of 2.86%, 5.11%, 7.67%, 10.19%, and 13.02% were prepared using fishmeal, soybean meal, and rapeseed meal as the main protein sources, and a mixture of fish oil and soybean oil in a ratio of 1:1 as the lipid source. A total of 600 juvenile P. clarkii with an initial body weight of (4.00±1.00) g was randomly divided into five groups (L1, L2, L3, L4, and L5 groups) with three replicates per group and 40 shrimps per replicate. They were fed five groups of experimental diets at 6:00 and 19:30 each day and cultured for 60 days. The experiment was carried out in an aquaculture pond (square, 1.0 m × 1.0 m × 0.6 m) at the Guangxi University.The results showed that as the dietary lipid level increased, the specific growth rate (SGR) and survival rate (SR) of juvenile P. clarkii first increased and then decreased and were the highest when the dietary lipid level was 7.67%. The feed conversion ratio (FCR) at first decreased before increasing again and that of the L3 group was significantly lower than that of the other groups (P < 0.05). Using the specific growth rate as an evaluation index, through broken-line analysis, the optimal dietary lipid level of juvenile P. clarkii was estimated as 6.82%. Dietary lipid levels had no significant effect on the moisture, crude protein, and ash contents in the muscle (P > 0.05). With the increase in dietary lipid levels, the cooking loss (CL) and crude lipid, polyunsaturated fatty acids (∑PUFA), and total amino acid (∑TAA) contents of the muscle showed an increasing trend. The content of eicosapentaenoic acid (EPA) in the L5 group was significantly higher than that in the other groups, and the docosahexaenoic acid (DHA) content in the L5 group was significantly higher than that in the L1 and L2 groups (P < 0.05). With increasing dietary lipid levels, muscle hardness, elasticity, cohesiveness, and gumminess decreased and there were no significant differences between the L1 and L3 groups (P > 0.05), whereas dietary lipid levels showed no significant difference in muscle saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA) contents (P > 0.05). The contents of umami amino acids (∑FAA), alanine (Ala), and aspartate (Asp) in the L5 group were significantly lower than those in the L1 group (P < 0.05).Under the conditions of this study, within a suitable range of fat content, growth performance increased with increased fat content; however, the addition of excessive fat cannot promote growth. According to the broken-line regression analysis of the specific growth rate, the optimal dietary lipid level was 6.82%. When the dietary lipid level was higher than 10.19%, the deposition and efficiency of muscle fat, muscle fat content, and nutrient loss increased, and the muscle texture index and Asp and Ala contents significantly decreased. The nutritional value, taste, delicious degree, and flavor of the muscle of P. clarkii were significantly decreased. As it does not affect the muscle quality of the shrimp, the dietary lipid content should not exceed 10.19%.Based on the analysis of various factors, the optimal dietary lipid content is beneficial to the healthy growth of juvenile P. clarkii and improves nutritional value and muscle quality. It is suggested that the dietary lipid supplemental level of juvenile shrimp should be 6.82%~10.19%. This study provides a theoretical basis for the scientific optimization of feed preparation for P. clarkii juvenile.

Suraiya Nazlia, Nurhayati Nurhayati, Ade Maya Riski et al.

This study aims to determine the effect of adding activated charcoal from tuna bones on the growth of gouramy. This research was conducted at the Integrated Laboratory of the Faculty of Fisheries, Abulyatama University, Aceh. The test fish used were gouramy seeds with a size of 2-3 g and 5-6 cm. This study used a non-factorial completely randomized design, consisting of four treatments and three replications, including A (control; without the addition of activated charcoal), B (addition of 1% activated charcoal in feed), C (addition of 2% activated charcoal in feed), and D (addition of 3% activated charcoal in feed) for 60 days of the rearing period. Fish are kept in an aquarium with a size of 60 x 40 x 40 cm as many as 10 fish per container with a water level of 30 cm. During the maintenance period, fish were fed twice a day at satiation. Parameters measured included survival, absolute weight and length growth, daily growth rate (LPH), and feed conversion ratio (FCR). The data were analyzed using analysis of variance (ANOVA). if significantly different, continue further testing using Duncan. The results showed that the addition of 2% tuna bone activated charcoal in feed affected growth performance including in absolute weight and length growth, SGR, and gave the best value on FCR and SR of 8.98 ± 0.20 g; 3.36±0.13cm; 2.60±0.11; 1.63; 100±0.00%. Keywords: activated charcoal; fish bone; growth; Osphronemus gouramy

MANCHI RAJESH, BIJU SAM KAMALAM, MANEESH KUMAR DUBEY et al.

A field study evaluated the safe loading density for live transportation of rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), yearlings in plastic bags of super-oxygenated water. The experimental fish (197.5 ± 40 g) were starved for 72 h and mildly sedated with clove oil (40 µL.L-1 for 2–3 min) before packing. Three loading densities of live rainbow trout (120, 170, 230 g.L-1) were packed in plastic bags containing 6 L of stream water and 10–12 L of medical-grade oxygen gas. Six replicate bags per loading density were then subjected to 10 h of transportation by road at ~10 °C. On arrival at the destination, important water quality indicators and fish survival were recorded from each plastic bag. With increasing fish loading density, there was a corresponding increase in the concentrations of carbon dioxide (CO2), total ammonia nitrogen (TAN), free ammonia (NH3), total dissolved solids (TDS) concentrations and specific conductivity in the transport water, and a decrease in dissolved oxygen (DO, R2 = 0.91-0.99). These differences in vital water quality indicators were significantly more in the 230 g.L-1 group. However, there was no mortality even at the highest loading density, as the critical water quality parameters did not cross the acute lethal thresholds for rainbow trout. Based on the findings, it is recommended that a loading density of 230 g.L-1 is safe for live transportation of rainbow trout yearlings in plastic bags over a transport duration of 10 h at ~10 °C, following adequate starvation and mild sedation.

A. Avadí, S. Cole, F. Kruijssen et al.

Abstract Fish is a key source of income, food, and nutrition in Zambia, although unlike in the past, capture fisheries no longer meet the national demand for fish. Supply shortfalls created an opportunity to develop the aquaculture sector in Zambia, which is now one of the largest producers of farmed fish (Tilapia spp.) on the continent. In its present form, the aquaculture sector exhibits a dichotomy. It comprises, on the one hand, a smallholder sector that mainly produces for and supplies within local markets, and on the other hand, a burgeoning larger-scale commercial sector consisting of a small number of pioneering lead firms who are (re)shaping how the value chain supplies domestic, mainly urban, markets. A notable challenge confronting the development of the aquaculture value chain in Zambia is ensuring that the larger-scale commercial sector can continue to grow and generate economic benefits for the country, while simultaneously safeguarding inclusive and sustainable growth of smallholder production systems. An in-depth, mixed-methods aquaculture value chain study was carried out in Zambia in 2017 that aimed at providing relevant stakeholders with pertinent information on the value chain's contribution to economic growth and its inclusiveness, as well as its social and environmental sustainability aspects. In this article, we present some key findings from the study to shed light on how the sustainability of smallholder production systems could be enhanced while preserving the growth trend of larger producers in an inclusive way. The study found that the value chain is contributing positively towards economic growth in the country. Smallholder farmers classified as “semi-subsistence” and “commercial” face several albeit somewhat different constraints to production, thus influencing their “sustainability” status. Semi-subsistence smallholders achieve positive (yet negligible) profit margins, and their production system is not environmentally sustainable and the value chain that supports them performs sub-optimally on several social markers. The “commercial” smallholder system is more economically viable and environmentally sustainable. The study juxtaposes these findings with those from the analysis of larger pond and cage-based systems to point to a set of key options Government, research, and development organisations could consider to support smallholder farmers and enhance the sustainability of the semi-subsistence smallholder production system in particular, without overlooking the whole system.

Mang-mang Wang, Hui-xing Guo, Yang-yang Huang et al.

This research is aimed at evaluating the effects of leucine supplementation on muscle fibers growth and development of blunt snout bream through a feeding trial and a primary muscle cells treatment. An 8-week trial with diets containing 1.61% leucine (LL) or 2.15% leucine (HL) was conducted in blunt snout bream (mean initial weight=56.56±0.83 g). Results demonstrated that the specific gain rate and the condition factor of fish in the HL group were the highest. The essential amino acids content of fish fed HL diets was significantly higher than that fed LL diets. The texture (hardness, springiness, resilience, and chewiness), the small-sized fiber ratio, fibers density, and sarcomere lengths in fish all obtained the highest in the HL group. Additionally, the proteins expression related with the activation of the AMPK pathway (p-Ampk, Ampk, p-Ampk/Ampk, and Sirt1) and the expression of genes (myogenin (myog), myogenic regulatory factor 4 (mrf4) and myoblast determination protein (myod), and protein (Pax7) related to muscle fiber formation were significantly upregulated with increasing level of dietary leucine. In vitro, the muscle cells were treated with 0, 40 and 160 mg/L leucine for 24 h. The results showed that treated with 40 mg/L leucine significantly raised the protein expressions of BCKDHA, Ampk, p-Ampk, p-Ampk/Ampk, Sirt1, and Pax7 and the gene expressions of myog, mrf4, and myogenic factor 5 (myf5) in muscle cells. In summary, leucine supplementation promoted muscle fibers growth and development, which may be related to the activation of BCKDH and AMPK.

J. Bell, A. Ganachaud, P. Gehrke et al.

Ginna M. Chacón, Alberto Arias-Pérez, Ruth Freire et al.

The banded carpet shell Polititapes rhomboides is a fishery resource and a suitable candidate for the development of native clam aquaculture in Europe. Here, we analyzed nine microsatellite loci in wild samples to provide estimates of genetic diversity and population differentiation for NW Spain, the main production area of this clam. We also analyzed wild-caught broodstock and hatchery-reared seed to investigate the genetic consequences of seed production for stock enhancement purposes by mass spawning. We examined the seed sample as a whole (total seed), but also subdivided it into three size classes to assess the genetic consequences of size grading. While wild samples, broodstock included, displayed minimal or no genetic differences, the total seed showed a reduction in allelic richness (12–24 %) and a significant level of differentiation (FST = 0.026−0.043) with respect to wild samples. After performing parentage assignment, we detected a drastic reduction in the effective number of breeders (Ne) compared to the census number (85 %), and an inbreeding rate of 0.036 per generation. The low Ne and high inbreeding rate were mainly due to high variance in reproductive success. The seed size classes also showed a decrease in allelic richness and significant genetic differentiation, but we did not find significant differences in parental contribution to each size class. Our results may help the genetic-assisted management of wild populations, give insight into the genetic composition of the seed produced by mass spawning and provide a basis for the development of more effective hatchery practices and sustainable stock enhancement programs in P. rhomboides.