Factors affecting the reproductive efficiency in crayfish: implications for aquaculture

In recent years, crayfish aquaculture industry has been developing rapidly in different regions of the world. Crayfish aquaculture is often carried out in dams, lakes and extensive pond systems. There is an increasing demand for crayfish juvenile in aquaculture sector. Therefore, it is important to know which factors affect reproductive efficiency in crayfish. In the present review, factors affecting the reproductive efficiency of crayfish are divided into two main sections, external and internal factors. Dietary lipids, phospholipids, highly unsaturated fatty acids, protein and amino acids, vitamins and carotenoids are important external factors affecting broodstock crayfish reproduction. In addition, various external (i.e. female size, stocking density, temperature, photoperiod, sex ratio) and internal (i.e. endogenous hormones) factors affect the reproductive efficiency in crayfish. This study reviews the present knowledge with the purpose of realizing the factors that are important to reach optimal crayfish nutrition, maturation and reproduction (i.e. pleopodal egg number and quality). This review will particularly be useful for crayfish farmers and crayfish hatchery units.     

A review of the biophysical properties of salmonid faeces: implications for aquaculture waste dispersal models and integrated multi-trophic aquaculture

Knowledge of the quantitative and qualitative properties of salmonid faeces is necessary for aquaculture waste dispersal models, and the design of integrated multi-trophic aquaculture (IMTA) systems. The amount and proximate composition of salmonid faeces can be estimated using a mass-balance, nutritional approach. Indigestible components of salmonid diets have the potential to affect faecal 'cohesiveness' or 'stability'. Nutrient content and density of faeces can vary depending on diet and submersion time. Faecal density has a greater influence on settling velocity than faecal size. Published settling velocity data on salmonid faeces are highly variable due to differences in fish size, rearing systems, collection time, water density, methodology, the mass fraction tested and diet. Most faecal settling data used in published salmonid waste dispersal models are rudimentary and recent information suggests that such models are highly sensitive to this input. The design of open-water IMTA systems and estimation of nutrient capture and recovery from co-cultured filter feeders is difficult due to limited information on particle size, digestibility, settleable and non-settleable mass fractions of salmonid faeces at cage environments. Implications of faecal properties on the accountability for the effects of aquaculture nutrient loading are discussed.     

Aquaculture ethics: A systematic quantitative review and critical analysis of aquaculture ethics scholarship

This paper investigates the ethical values, moral principles, methods and reform proposals in aquaculture ethics scholarship to develop a comprehensive and balanced list of aquaculture ethical principles. A Systematic Quantitative Literature Review methodology is employed to parse 150 journal articles on aquaculture ethics. Methodologies, specific ethical values, broad principles, recommended reforms and trends over time are quantified and assessed. Through analysis of invoked values and recommended reforms, six core marine economy ethics principles are identified: Environmental Protection, Fairness, Stakeholder Participation, Harm Prevention, Beneficence and Trustworthiness. A comprehensive multidimensional legitimacy model is employed to uncover ethical gaps and identify promising areas for future aquaculture ethics research.     

Levels of domestication in fish: implications for the sustainable future of aquaculture

The agricultural world today is dominated by a few domesticated mammal species, that is, animals modified from their wild ancestors through selective breeding in captivity for traits beneficial to human usages. As a result, a clear dichotomy exists between wild (from hunting) and domesticated mammals (produced in farms) used for human consumption. Similar to agriculture, aquaculture is often viewed as the only solution that can provide more fish products given that harvesting wild stocks have reached an upper limit. Aquaculture is considerably younger than agriculture relying on natural sources to farm numerous species. To better describe the diverse strategies for fish production, we propose a new classification comprising five levels of ‘domestication’ with 1 being the least to 5 being the most domesticated. Our classification places 70% of the 250 farmed finfish species recorded in the 2009 FAO database into levels 1, 2 and 3 representing a transitory form of fish production dependent on the availability of the wild resource. In contrast, only a few species, or more accurately populations, can be considered truly domesticated, similar to cattle or sheep. Based on this classification, two scenarios for the future of aquaculture are discussed: either the industry focuses on few truly domesticated species, similar to the path taken by agriculture, but avoiding its negative impacts or aquaculture proceeds with inter‐specific diversification by focusing primarily on the domestication of native species.     

Advances in economics of marketing and implications for aquaculture development

Abstract

This paper builds on an earlier review by Kinnucan and Wessells (1997) by discussing in some detail product differentiation, market integration, and generic advertising. The goal is to identify approaches and findings in each topical area that would appear to have relevance for aquaculture. Selected applications are given to highlight principles and to demonstrate usefulness.     

Goods and services of extensive aquaculture: shellfish culture and nutrient trading

Bivalve shellfish play an important role in top-down control of primary symptoms of eutrophication. This short-circuits the process of organic decomposition and promotes an enhancement of underwater light climate, improved oxygenation of bottom water, and restoration of submerged aquatic vegetation. This review analyses this ecosystem service as a potential actor in watershed-level nutrient credit trading programmes and explores the possibilities of implementation of such programmes in Europe. We examine the different components of the issue, including the eutrophication status of European coastal waters, legal and management instruments, and the use of mathematical models at both the ecosystem and farm scales to evaluate the potential removal of nitrogen by cultivated shellfish such as oysters, mussels, and clams. The annual European bivalve shellfish production of over 700,000 metric tons is estimated to generate a nitrogen removal of 46,800 t year^?1, equivalent to 14 × 10⁶ population equivalent, and a minimum value of 507 × 10⁶ €. We discuss future directions for this topic in Europe, drawing from ongoing research in the USA and elsewhere, in the light of the twin challenges of European aquaculture expansion and implementation of EU directives.     

Stringency of environmental regulation and aquaculture growth: A cross-country analysis

During the last three decades, aquaculture has been the fastest growing animal-food-producing sector in the world, accounting for half of the present seafood supply. However, there is a significant growth disparity among aquaculture-producing countries. The reasons why some countries have achieved remarkable growth in aquaculture while others have stagnated or even declined have not been determined. In this article, we investigate whether environmental regulations have an impact on aquaculture growth. Using a cross-country regression analysis, we show that stringent environmental regulations are negatively related to aquaculture growth, whereas GDP growth has a positive effect. Countries often face a difficult balancing act between growth and environmental considerations when devising regulations. Our empirical results suggest that stricter environmental regulations in developed countries have contributed to lower growth rates and that these countries are falling behind emerging and developing economies that have more lenient environmental regulations.     

Introduction of genetic engineering in aquaculture: Ecological and ethical implications for science and governance

Within aquaculture, genetic engineering (GE) is emerging as a powerful method for breeding of fish and shellfish, and for developing alternative sources of feed and vaccines to combat diseases. On the other hand, the use of GE in aquaculture raises ecological, ethical and economic concerns. For instance, genetically modified (GM) feed could be spread to the aquatic environment and consumed by other marine organisms, and horizontal gene transfer may conceivably occur from DNA in feed or vaccines to a recipient genome or by faeces to the environment. Numerous reports have described beneficial effects such as viral disease resistance following DNA vaccination. However, side effects, such as activation of other genes than those which are central in immune defence mechanisms, may occur and warrant further investigations. In order to achieve sustainable introduction of GE, it is crucial that appropriate scientific investigations and ethical considerations are done prior to large-scale introduction of GE products such as DNA/GE vaccines and GM feed in commercial fish farming. This may result in a solid basis for the avoidance of potentially undesirable health and environmental effects. If GE can help make aquaculture a sustainable industry, this opens the possibility of positive market and consumer responses. This can best be achieved by involving the stakeholders from the conceptual stage to the commercial stage by facilitating a transparent process whose purpose is to inform research, to identify decision stakes, and to influence design, adoption and implementation of pro-active policy.     

Population genetic structure of lumpfish along the Norwegian coast: aquaculture implications

The potential for genetic contamination of stocks arising from translocation and subsequent release or escape of translocated and/or genetically mixed stocks may be a significant risk to wild populations. In this context, we undertook a population genetic survey of stocks of lumpfish (Cyclopterus lumpus) along the Norwegian coast to establish the existing genetic population structure, which will aid the development of policy of the species’ use as cleaner fish in salmonid aquaculture. This was done by using 14 microsatellite loci and 287 specimens collected at five fishing grounds, covering most of the Norwegian coastline from south to north, with additional 18 samples of first-generation reared fish from a fish farm outside Tromsø (North Norway). Overall, there was no indication of significant spatial genetic structuring or of positive correlation between geographic and genetic distance among the wild lumpfish samples. These results suggest that, should translocated individuals escape from aquaculture in Norway, this will probably have little to no impact on the genetic composition of the local fish population.     

Comments on the development of techniques for management of environmental quality in aquaculture

Management procedures which improve or stabilize environmental quality in aquaculture ponds are needed. The development of such procedures requires knowledge of quantitative relationships among two sets of variables: (1) fish production and specific aspects of environmental quality and (2) the management procedure and environmental quality. The specific changes desired in environmental quality must be identified, and the effect of a given degree of application of a management procedure on both environmental quality and aquacultural production must be ascertained. Management procedures must produce predictable results at a reasonable cost.

Environmental factors which must be considered in managing water quality in fertilized ponds and in ponds in which feeds are applied are discussed. Some examples of the development of successful environmental quality management techniques are provided and topics for future research are mentioned.     

Genetic relationships among members of the Ichthyobodo necator complex: implications for the management of aquaculture stocks

Abstract Ichthyobodo necator (costia) is a common and important flagellate parasite that infests the skin and gills of many freshwater and marine fish. Costia infestations are often fatal and cause significant aquaculture losses worldwide. Recently it has been demonstrated that Ichthyobodo is a multispecies complex with differing host preferences. Knowing if those species have broad or narrow host specificity has important implications for the management of costia. To address the question of host specificity, genomic DNA was isolated from Ichthyobodo trophonts collected from rainbow trout, Oncorhynchus mykiss, koi, Cyprinus carpio, mirror carp, C. carpio, goldfish, Carassius auratus, channel catfish, Ictalurus punctatus, swordtail, Xiphophorus helleri, and Japanese flounder, Paralichthys olivaceus. The small subunit ribosomal RNA (SSU rRNA) gene from each isolate was analysed with previously published Ichthyobodo sequences using Bayesian phylogenetic methods. The internal transcribed spacers (ITS) from six isolates were also PCR-amplified, cloned and sequenced. Both the SSU rRNA phylogenetic analysis and the ITS rRNA sequence data support grouping the 22 Ichthyobodo isolates examined into a complex of nine different species. Many of these species were frequently isolated from multiple hosts, indicating that exchange of infested fish from one region to another has a high potential for spreading the disease. In one instance, the same species was obtained from marine and freshwater fish, further suggesting that certain Ichthyobodo species may not be limited by salinity.     

水产养殖对环境的影响及其防治对策分析

介绍了水产养殖的类型,水产养殖所形成的废物输出,水产养殖对环境造成的影响,以及防治水产养殖污染的途径。通过综述分析,对水产养殖与环境之间的关系有较为深入的了解,有利于相关部门制定相应的政策,开展相应的研究等工作。     

L-肉碱对水产动物生长免疫与水体生态环境的影响

在水产动物饲料中添加适量的L-肉碱,可以促进生长发育,改善身体组分;还能提高饵料中蛋白的利用率,增加氮的沉积,减少氨氮的排放,改善水体生态环境;同时对提高机体的免疫功能和抗应激能力也有促进作用。     

基于FPGA的水产养殖环境无线测控模块设计

针对我国水产养殖无线远程信息测控多以成熟单片机为核心控制主件,不易满足行业特殊接口需求以及缺乏独立核心控制器的现状,项目以标准化及芯片自主化为最终目的,提出基于现场可编程门阵列(FPGA)为核心的实现方案,尝试性设计了一种较为通用的、可实现AD转换、数字接口、控制输出和驱动以及养殖现场数据存储和远距离数字通讯的测控模块。通过对水产养殖领域环境信息的无线测控模块各主要环节的研究设计,以模块到系统的FPGA原型功能验证方式,实现了现场模块对水产养殖的温度、溶氧信息的远距离测量和控制。系统测试和板级实验结果表明,该设计可以满足低成本、接口可扩展及标准化核心控制器的水环境测控模块需求。     

An evaluation of the role and impacts of alien finfish in Asian inland aquaculture

Asia dominates global aquaculture production accounting for over 80% of the total and the mainstay in Asian aquaculture is finfish. Over the years, Asia has experienced a number of inter‐continental and intra‐continental transfers/introductions/translocation of finfish species, between nations and watersheds, beyond their natural range of distribution, primarily for aquaculture development. In this article all such species are referred to as alien species. An attempt is made to evaluate the importance of the production of alien species in selected Asian nations, using statistics of the Food and Agriculture Organization. Also, negative effects, if any, based on literature surveys, of alien species in relation to displacement of indigenous species, and on biodiversity and/or genetic diversity together with associated pathogen transfers are evaluated. The major alien species, based on their significance to Asian inland aquaculture considered, are the tilapias, catfish, Chinese and Indian major carps and common carp. It is estimated that currently alien species account for nearly 12% of the cultured finfish production (2.6 million tonnes) in Asia, valued at US$ 2.59 billion, and the contribution exceeds 40% when Asian countries excluding China are taken into consideration. Inland finfish aquaculture in some Asian nations, such as Indonesia and the Philippines, is predominated by alien species, and in some others, e.g. Bangladesh and India, the contribution from alien species has been increasing steadily. It is suggested that overall alien finfish species have done little ecological harm to native flora and fauna. However, in the wake of increasing anthropogenic development taking place in watersheds the resulting environments are often made unconducive to indigenous species but not to some alien species, thereby potentially and indirectly making the latter invasive.     

水产养殖业预防性抗生素的大量使用:一个日益严重的人与动物健康以及环境问题

正水产养殖业的迅猛发展导致了一系列对环境和人类健康有害的行为的传播,这一点可以从业内普遍且无限制地使用预防性抗生素得到证实,特别是在一些普及养鱼的发展中国家,为防止鱼类遭受细菌感染形成了不健康的生产方式。多种抗生素的大量使用,包括一些医学上有益但不可降解的抗生素     

Correction to: Population genetic structure of lumpfish along the Norwegian coast: aquaculture implications

The original version of this article unfortunately contained an error where the figure caption for Figures 3 and 4 was mixed.     

Optimization of fertilization rate for maximizing periphyton production on artificial substrates and the implications for periphyton-based aquaculture

The effects of four rates of application of fertilizer, with cow manure (3000 kg ha⁻¹), urea (100 (kg ha⁻¹) and triple super phosphate (TSP) (100 kg ha⁻¹) (treatment F)), treatment F × 0.5 (treatment 0.5F), treatment F × 1.5 (treatment 1.5F) and treatment F × 2 (treatment 2F), on periphyton, plankton and water quality in tropical freshwater ponds were studied. The highest periphyton biomass in terms of dry matter (3.27 mg cm⁻² substrate), ash-free dry matter (2.06 mg cm⁻² substrate) and chlorophyll a (7.49 µg cm⁻² substrate) developed in treatment 1.5F. The ash content of periphyton was lower in treatment 1.5F (38% of dry matter) than in other treatments (57–66% of dry matter). Total ammonia and chlorophyll a of water increased with fertilization rate. Treatment 1.5F (cow manure, urea and TSP at rates of 4500, 150 and 150 kg ha⁻¹ respectively) appears to be the optimum, yielding high quantity and quality periphyton. By supplying a substrate area for periphyton equivalent to the pond surface, it was estimated that this level of fertilization could support a fish production of around 5000 kg ha⁻¹ y⁻¹, without recourse to supplementary food.     

Role of salinity in the dissolution rates of CaCO3 and its implications for aquaculture liming

This work aimed at assessing the role of salinity in the dissolution rates of CaCO₃, discussing its implications for aquaculture liming. A simplified formula of artificial seawater without HCO₃^? was initially prepared. Four batches of 10 L of diluted artificial seawater (salinity = 3.3 g/L) without HCO₃^? were prepared. Sixteen Erlenmeyer flasks were filled up with 2 L each of the diluted artificial seawater without HCO₃^?. Besides, 16 other 2,000‐ml Erlenmeyer flasks were filled up with 2 L of distilled water (freshwater). The experimental treatments were formed by applying increasing amounts of analytical‐grade sodium bicarbonate (NaHCO₃) upon brackish water and freshwater. Accordingly, four initial levels of total alkalinity (TA) have been set up as follows: 4–6, 33–35, 62–63 and 120–122 mg/L. Next, approximately one gram of analytical‐grade calcium carbonate (CaCO₃) was applied onto each flask. Water's pH, TA and calcium concentration were determined weekly over a 7‐week period, by appropriate methods. For a same initial TA, TA increase over time after CaCO₃ application was lower in the brackish water flasks than in the freshwater ones. This was especially clear for moderate (63 mg/L) and high (120 mg/L) alkalinities. It was concluded that brackish and saline waters used for aquaculture would only benefit from CaCO₃ liming if their alkalinities were lower than 60–80 mg/L.