Aquaculture, Fish and Fisheries最新文献

Cage fish farming, a recent development in aquaculture, has enhanced fisheries production due to its higher stocking densities than traditional pond and open-water systems. Although it can enhance production, the system can pose biodiversity threats when there is an unintentional or intentional release of stocked fish into the wild. In this review, we examine the expansion of Nile tilapia (Oreochromis niloticus L.) cage aquaculture in Africa and the potential threats that this may have on congeneric Oreochromis species. Threats such as interspecific competition, disease transmission and hybridisation, which are drivers of genetic diversity loss among native fish populations, have been reported. However, most studies have focused on investigating cage fish production, water quality and the associated economics, but research assessing the genetic and ecological impacts imposed by the escaped fish from cages on native species is still limited across African countries. While direct evidence of hybridisation due to cage fish farming is lacking, genetic mixing of Nile tilapia with native Oreochromis species has been reported in some African water bodies. Further, only Egypt, Kenya and Uganda have functional Fisheries and Aquaculture regulations for guiding the aquaculture activities. Thus, there is an urgent need to institute regulatory frameworks that not only provide clear guidelines on aquaculture production but also balance between environmental conservation and economic sustainability.

Global trade in marine and aquaculture fishery products reached $186 billion by 2022, reflecting a 63% increase over the past decade and contributing to economic growth and supporting Sustainable Development Goals 1, 2 and 14. Tanzania's exports of processed small pelagic products surged to $3.9 million in 2023–2024, driven by rising demand in African markets, while exports of crustacean products to the global north reached $11.8 million. Despite the sector's contribution to economic growth and livelihoods, the influence of marine trade on microeconomic development and income distribution among actors remains underexplored. This study fills this gap by examining the distribution of trade benefits and associated inequality in Tanzania's seafood trade. The study was conducted at four landing sites in three coastal districts of Tanzania. The net income distribution approach, Lorenz concentration curve and Gini coefficient were used to analyse income distribution and inequality in seafood trade. Findings showed a significant gap in income and costs across actors in the small pelagic and crustacean value chains, with traders earning higher income than other actors. The Gini coefficients for the small pelagic and crustacean chains were 0.58 and 0.44, respectively, signifying greater income inequality among traders (aggregators and wholesalers), processors and fishers in both chains. The study recommends improving market infrastructure and institutionalising pre-trade agreements to ensure a fair distribution of benefits within the sector.

As part of an ongoing study aimed at evaluating the contribution of green turtle hatchlings to the diet of predatory fishes in the Bijagós Archipelago, Guinea-Bissau, West Africa, several fish individuals were captured. Three of them were assigned to the genus Lutjanus Bloch, in 1790. These fish individuals were identified using DNA barcoding along with photographic inspection of relevant characters, revealing to be Cubera Snapper Lutjanus cyanopterus (Cuvier, 1828), a species native to the west Atlantic. This finding is discussed in relation to other occurrences of this species in the east Atlantic.

Atlantic salmon (Salmo salar) are globally cultured fish that are typically fed high protein and high lipid diets. Increasing ingredient diversity in salmon feeds is important to ensure that high-quality feeds are sustainable and are available at a reasonable cost for commercial producers. While fishmeal was traditionally added as the prime protein ingredient, today's salmon diets contain plant-based, marine and animal-by-product ingredients. This study examined a single-cell protein ingredient torula yeast (SylPro, Arbiom Durham NC) as an alternative protein source for Atlantic salmon. There were no differences in FCR, or weight gain, compared to fish fed a commercial like diet (p > 0.05). Similarly, whole body proximate composition did not differ among the treatments (p > 0.05). Diet digestibility was also examined, and there were no significant differences among treatments (p > 0.05). The diets with torula yeast tended to have smaller particle sizes compared to the reference diet with the 10% diet having 50% of the particles below 60 µm (p < 0.01). These results indicate that torula yeast added up to 20% of the diet is an acceptable protein ingredient for inclusion in Atlantic salmon diets.

Several articles over the last two decades have provided data, analyses and interpretations that suggest there are significant impacts of pathogens transmitted from farmed salmon on wild Pacific salmon populations in British Columbia (BC), the westernmost province of Canada. Because disease is a normal part of all animal populations, there is always a potential for pathogen transfer between animal populations that interact. However, the evidence is weak that pathogens transmitted from farmed salmon cause significant impacts on wild salmon populations. We provide additional data and alternative interpretations of the available evidence to show that (i) many studies overestimate the risk of pathogens transmitted from farmed salmon to wild Pacific salmon, (ii) these risks have not manifested as having significant impacts on wild Pacific salmon populations, and, therefore, (iii) the evidence better supports the conclusion that pathogens transmitted from farmed salmon are having no more than minimal impact on wild Pacific salmon populations. On the basis of this information, we hypothesize that removing open net pen salmon farms will have no detectable effect on wild Pacific salmon population productivity in relation to reference populations.

This study investigated the efficiency of nutrient film technique (NFT) aquaponic systems in enhancing the productivity of Nile tilapia (Oreochromis niloticus), African catfish (Clarias gariepinus), and leafy vegetables (lettuce, spinach and basil) under aquaponic conditions. The study was conducted for 9 weeks at the Maseno University Fish Farm in Kenya. Identical tilapia-based and Catfish-based NFT setups were used, whereas soil-based crop cultivation and earthen fishpond systems served as controls. Mono-sex male tilapia and catfish fingerlings were stocked at an initial average length of 10 cm and weight of 50 g. The fish were stocked at a density of 60 fish/m³ and fed to satiation on a 35% crude protein formulated diet twice a day, whereas crops were transplanted after being raised for 20 days in the nursery and when they had at least three fully developed leaves. Fish growth in the NFT system was significantly better than in pond-based systems for tilapia and catfish. Tilapia achieved a final weight of 175 g and a feed conversion ratio (FCR) of 1.44 in NFT, compared to a final weight of 129.86 g and an FCR of 2.1 in the pond-based system. Catfish had a significantly higher total yield in the earthen pond (15.4 kg/m³) than in the NFT system (12.5 kg/m³) (p < 0.05). Lettuce had significantly higher leaf area (179.9 cm²) and final yield (36 kg/m²) compared to spinach with leaf area (85.2 cm²) and yield (30.2 kg/m²), and basil with leaf area (38.0 cm²) and yield (5.7 kg/m²). The Tilapia NFT system demonstrated superior performance for fish and vegetable growth, performance and yield, water and nutrient use efficiency, and nitrogen recovery. This better performance is due to the better nutrient profile of tilapia waste compared to catfish and better adaptability to NFT systems compared to catfish.

From fertilisation to hatching, we investigated the embryonic development of hatchery-reared Murray cod eggs incubated at 20°C and determined the developmental stages. Twenty-eight readily identifiable stages with distinct morphological features were described and illustrated. Meanwhile, a simple and effective method for evaluating developmental competence at 1/2 epiboly was developed, which does not require the exhausting removal of egg chorion. Acute mortality was observed within 28 h post-fertilisation, indicating that critical stages may occur during this period. The presented results may provide vital information to improve hatchery practices.

This study investigated the effects of dietary ginger (Zingiber officinale) powder on the growth, feed utilisation, innate immune response, serum biochemical parameters and haematological health of walking catfish (Clarias batrachus) in a cage culture system. Four experimental diets were formulated: a control diet (C, commercial feed without ginger powder), and three treatment diets supplemented with ginger powder at 3 g/kg (T₁), 5 g/kg (T₂) and 7 g/kg (T₃) of the commercial feed. Triplicates of 30 fish (initial weight: 3.68 ± 0.05 g) were randomly assigned to the dietary treatments and fed twice daily to satiation for 56 days. At the end of the trial, fish in the T₃ group exhibited significantly higher (p < 0.05) weight gain (226.47 ± 2.61%) and specific growth rate (2.11 ± 0.01%/day) compared to the control group. Additionally, the feed conversion ratio (FCR) was significantly lower in T₃ (1.18 ± 0.01), with all ginger-supplemented groups showing improved FCR relative to the control. Haematological parameters such as white blood cell (WBC) count (5.17 ± 0.15 × 10⁹/L), lymphocytes (65.13 ± 2.33 × 10⁹/L), red blood cell (RBC) count (0.15 ± 0.01 × 10¹²/L), haematocrit (HCT; 1.90 ± 0.25%), MCH (49.33 ± 2.11 pg) and platelet (MPV) count (968.33 ± 2.40 × 10⁹/L) were significantly improved in T₃. Biochemical indicators such as alanine aminotransferase (ALT; 17.59 ± 4.19 U/dL), aspartate aminotransferase (AST; 160.76 ± 1.08 U/dL) and triglycerides (TGs; 44.83 ± 2.22 mg/dL) were significantly reduced in T₃, indicating improved liver function and lipid metabolism. Moreover, alkaline phosphatase (ALP) and respiratory burst (RB) activity, key innate immune markers, were significantly enhanced in T₃ compared to the control. These findings demonstrate that dietary supplementation with ginger powder, particularly at 7 g/kg (T₃), positively influenced growth, feed utilisation, immunity, serum biochemistry and haematological health in C. batrachus.

Aeromonas hydrophila, an omnipresent bacterium that infects a wide range of hosts, is responsible for massive mortality and significant financial losses among farm-raised fish species. To control bacterial diseases in aquaculture systems, inappropriate antibiotic therapy is commonly practised, leading to the development of antibiotic-resistant bacteria (ABR); using medicinal plants and/or extracts can be an alternative to antibiotics, thereby reducing dependency on antibiotics. Thus, a comprehensive prospecting into medicinal plant extracts to combat A. hydrophila infection in aquaculture is necessary. The immunostimulant characteristics of medicinal plants have generated a rising interest in their use in aquaculture. The present review examined the potential impact of plant extracts on the haematological, biochemical and immunological factors that might influence the general health of the fish as well as combat infection against A. hydrophila. The analysis revealed that the essential haematological parameters (haematocrit, haemoglobin, erythrocyte count and leukocyte count) and biochemical and immunological parameters (plasma glucose, cholesterol, triglycerides, albumin, total proteins, aspartate aminotransferase, alanine aminotransferase, phagocytic activity, respiratory burst activity and antioxidant activity) of fish were significantly improved when fish were fed with the extracts treated diet. Additionally, the growth parameters and survival rate of fish in the extract-treated group were found to be significantly increased subsequent to exposure to A. hydrophila. The findings emphasize the capacity of plant extracts to serve as eco-friendly substitutes for conventional therapies in aquaculture by enhancing fish health and resistance to diseases.