Aquaculture, Fish and Fisheries最新文献

Muskellunge are a valuable sportfish species which has been stocked throughout North America. Stocking is a strategy to generate angling opportunities by introducing species to waterbodies that otherwise would not have contained the fish, such as impoundments and reservoirs. Therefore, understanding the ways fish interact with different waterbodies is critical for managers to understand. To that end, we utilized a year-long passive telemetry study with muskellunge in a reservoir known for its muskellunge angling. Additionally, we employed temperature loggers to track lake temperatures. We found that smaller female muskellunge were more resident at sites compared to similar-sized males, although fish did not exhibit site-specific preferences. We also found that fish moved high distances over the course of the year without time-specific differences. Furthermore, we found evidence that muskellunge was selected for thermal refuges in the reservoir; however, in summer, when water temperatures were elevated, fish inhabited water, which has been shown to increase incidental mortality. The results of this study indicate a need for muskellunge managers, especially in reservoirs, to consider water temperature in angling regulations. Additionally, our results highlight a need for adding habitat structure in reservoirs and altering stocking densities of fish. Collectively, these results will help inform managers on muskellunge spatial interactions within a reservoir and achieve management goals.

Microalgae offer a sustainable source of omega − 3 fatty acids that can replace fish oil in aquafeeds, but the nutritional benefits are not always clear, particularly when microalgae are used as complete oil replacements in starter feeds. We compared the survival, growth, omega − 3 deposition and composition of the gut microbiota of juvenile mixed-sex Nile tilapia (Oreochromis niloticus) that had been fed over a 3-month period on six isonitrogenous, isolipidic and isocaloric aquafeeds that varied only on the contribution of fish oil, soya oil and microalgae (Schizochytrium) oil as lipid sources. Survival was not affected by diet, but fish fed a diet where the entire oil component (5%) was replaced by microalgae oil grew twice as fast as fish fed plant oil or a mixture of plant and fish oil. Dietary omega − 3 content was strongly correlated with omega − 3 deposition in the fish fillet. Complete replacement of fish oil by plant oil caused a significant decrease in the abundance of Peptostreptococcaceae and an increase in the abundance of Aeromonadaceae which is often associated with an inflammatory response in the fish gut. In contrast, when fish and soya oil in the reference diet were replaced by 100% microalgae oil, an increase in Mycobacteriaceae was observed. Our study indicates that Schizochytrium oil can be used to improve the growth of Nile tilapia and increase its omega − 3 content without any of the detrimental effects on the gut microbiome typically associated with some plant oil replacements.

This review was aimed to summarize the extent and causes of fish post-harvest losses (FPHLs) in Sub-Saharan African (SSA) countries and suggests the necessary intervention measures to narrow the gap between demand and supply. Globally, an estimate of 10–12 million tons of fish is lost per year. FPHLs in SSA are higher than those in other parts of the world. In SSA, the values of fisheries are estimated at 24 billion USD, 1.26% of the GDP of all the African countries and 6% of agriculture GDP. The vast majority of FPHLs in SSA occur at the production (39%), handling (36%), distribution (13%), processing (7%) and consumption (5%). The major factors that cause FPHLs in SSA were long time spent in hauling of fishing gears, spoilage, size discrimination, species preferences, operational losses, animal predation, poor handling practices, lengthy duration of fishing cycle, failure to use ice, lack of storage facilities, lack of transportation and insect infestation. FPHLs amount one third of total production and financial losses of 2–5 billion USD in SSA countries. Furthermore, volarization of fish waste and converting waste into useful substances is a promising approach to reduce fish waste. It can be recommended that improving fish production, live fish handling, processing, preserving, and marketing in SSA could narrow the gap between fish demand and supply.

Bluespotted seabream Pagrus caeruleostictus, a member of the family Sparidae, is one of the high-priced seabream species in Ghana. Although the fish has been exploited in the Gulf of Guinea for over hundreds of years, there is scanty information on the state of the fish stock. Hence, we sought to investigate the exploitation status and aspects of the reproductive biology of the species by collecting monthly length and weight data for 18 months (February 2016 to July 2017). These data were fitted to growth and mortality models. The sexual maturity, fecundity and spawning seasons were also determined within the same period. The growth model of the fish revealed that the asymptotic length (L_∞) and growth coefficient (K) values determined were 52.7 cm (total length) and 0.52 year⁻¹, respectively. The mortality models also showed that the fishing mortality (F) of the fish was 2.20 year⁻¹, whereas its natural mortality (M) was 0.83 year⁻¹, with F/M > 0.5 indicating that the fish is over-exploited. The lengths at first sexual maturity (L_m) of the males and females were 36.2 and 28.0 cm, respectively. Pagrus caeruleostictus, which was found to be highly fecund, had two spawning periods in a year, occurring in September and March, both with unimodal ova diameter frequency distributions. Based on these findings, we recommend that catch limits and other appropriate management measures (e.g. temporal and spatial closures) should be prescribed for the seabream fishery in the Gulf of Guinea to ensure the sustainability of the fishery.

In the 1980s, Artemia franciscana from San Francisco Bay (SFB) was introduced into Kenyan saltworks, where it has colonized and established stable populations. However, little is known about its biology, particularly with respect to its parental SFB population. This study compared the salinity tolerances of Kenyan (KEN) population, their SFB progenitors and those of Great Salt Lake (GSL) populations. Growth and survival of these A. franciscana populations were evaluated under varying salinity levels in a laboratory set up. A. franciscana nauplii were cultured at a rate of 1 nauplii/mL in 36 Erlenmeyer flasks and fed microalgae (Chaetoceros sp.) at 1.5 × 10⁶ cells/animal/day for 8 days. Survival was evaluated daily and survivors were fixed in individual vials with Lugol solution. The total length of each fixed A. franciscana nauplii specimen was measured under a compound microscope. All populations were susceptible to salinities greater than 100 g/L. Compared with the parental SFB population, the KEN population exhibited significantly reduced survival and growth at 140 g/L, suggesting a narrower salinity tolerance range. These findings underscore the need for further studies focusing on other physiological parameters, abiotic factors and genetic characterization to confirm whether the KEN population is experiencing ecological adaptation. This will contribute to the optimization of Artemia practices in various salinity environments as a result of climate change.

The increase in hard artificial structures in the marine environment is contributing to ocean sprawl. As well as adding hard structure to the seabed, mussel aquaculture adds rope droppers and anchor lines to the water column, where such structure would otherwise be absent. This paper aims to monitor the effects of mussel headlines on the pelagic fish community over time, as well as to investigate whether there is an interaction between the age of cultivated mussels with the number of epibiota species and the abundance of pelagic fishes. Two surveys were carried out: a time series monitoring survey to assess whether the mussel headlines change the surrounding fish species relative to control areas over time, and a fish aggregation device effect survey to investigate whether older and larger mussels support greater abundances of pelagic fishes and epibiota. The most abundant fish species was Atlantic horse mackerel, Trachurus trachurus, with significantly greater numbers recorded around ropes growing older mussels. Results from the surveys show that the physical farm infrastructure has provided a substrate for colonisation by a variety of epibiota: A total of 21 species were recorded growing on the mussel ropes. Furthermore, the older and larger the mussels become, the greater the numbers of epibiota taxa that can colonise, coupled with a greater abundance of pelagic fish recorded around the ropes. The sustainable development of offshore Blue Industries is essential to produce renewable resources. This study brings essential evidence for marine managers and regulators that offshore mussel farming can provide benefits for pelagic and benthic species of both conservation and commercial importance while producing sustainable protein to feed a growing population.

Male lobsters (Homarus americanus) harvested as ‘quarters’ (1.25 lbs/567 g) in two time periods (winter, N = 16, and summer, N = 25) of 2018 are examined. Indicators of quality data were collected for each lobster, including non-invasive measures (shell hardness, carapace length, sex, live weight, colour, body shape, location, time of harvest) and invasive measures (blood protein [BRIX] level at time of harvest, cooked weight, meat content). Lobster BRIX levels are used as a proxy for actual meat content and as the key indicator of lobster quality. A regression model of the relationship between the natural logarithmic transformation of lobster BRIX levels (independent variable) and meat content yield as a percentage of shell-on (uncooked) weight (dependent variable) is presented. The objective of this study is to evaluate alternative BRIX-based decision rules for achieving desired meat content percentage yields for preparing shipments to global markets. The present study found that BRIX-based grading rules can be determined to achieve minimum desired meat yields, minimum overall shipment yields and minimum proportions of shipments below desirable yield rate. For a minimum desired industry threshold of 24% meat content, the preferred BRIX value rules are (i) 8.5 mg mL⁻¹ and (ii) ‘9 mg mL⁻¹ with 10% plus condition’. These rules improve the admissibility of samples and reduce the risk of below desirable meat yields.

Research-based knowledge is essential for effective conservation and restoration of threatened aquatic species and habitats. Here, our aim was to gather this knowledge on the lake-dwelling grayling (Thymallus thymallus), typically a riverine fish. Such atypical populations are particularly vulnerable to anthropogenic impacts, including fishing pressure, climate change, eutrophication and waterway construction, some of which affect especially the early life stages. However, there is little information available to guide management and conservation of grayling in lakes. Accordingly, we assessed characteristics of the nursery areas in the threatened grayling population of Lake Puruvesi (eastern Finland). In particular, we used beach seines in two consecutive years to sample lakeshore sites (including islands) that were a priori presumed suitable for grayling. We assessed the occurrence of grayling fry (larvae and post-larvae <40 mm in length) regarding depth, year, the site's exposure (fetch), bottom shear stress, substrate coarseness and shoreline's north–south orientation. Overall, we found grayling fry in low numbers at every fourth site, with the sites’ exposure and dominant substrate coarseness being most relevant variables. In particular, more exposed sites (i.e. with higher fetch values) and fine-grained substrates dominated by sand or gravel had more grayling fry. Average depth, bottom shear stress or shoreline orientation along the north–south axis did not have a significant effect. Together, the results suggest that the most important nursery areas for lake-dwelling grayling are lakeshore zones that are barren and exposed. Hence, the sites share characteristics with those used for reproduction by the more common riverine grayling. We hope that these findings will facilitate lake-dwelling grayling's management and conservation efforts.

Biofluorescence is widely documented in marine organisms, yet few studies exist for decapods. After observing the king crab Paralithodes camtschaticus biofluoresces, we carried out studies on two separately maintained groups of male crabs under controlled conditions. Hyperspectral imaging on Group 1 (n = 18) examined the exoskeleton, whereas fluorospectrometry examined the hemolymph of Group 2 animals (n = 19). Both groups were investigated for fluorescence signals before and after exposure to a live shipping transportation simulation. The spines, chelae, eyestalks and cervical grooves of the cardiac region of P. camtschaticus fluoresce in the green spectra (∼500 nm), while the arthrodial membranes of the joints fluoresce in the red spectrum (∼680 nm). After the shipping simulation, we observed a significant decrease in fluorescence in the eyestalks (p = 0.009), while the cervical grooves showed a less significant change (p = 0.01). The hemolymph examined with 21 excitation wavelengths (250–350 nm) emitted fluorescence in ∼400–550 nm spectrum. We found a significant increase (p < 0.05) in fluorescence for 16 excitation wavelengths after transport simulation. The results presented in this study indicate that king crab fluorescence changes due to external stimuli. Fluorospectroscopy or hyperspectral imaging technology may serve as an effective early indicator of preclinical stress in these commercially important decapods.

The major carp Rohu (Labeo rohita) is a prime freshwater aquaculture species across the Indian subcontinent that faces various production-related issues associated with water quality parameters. The present study examined the effects of three different doses of NH₃ (T1 = 1 mg/L, T2 = 2 mg/L and T3 = 3 mg/L) on cellular (gill ultrastructure), physiological (growth and oxygen consumption rate), biochemical (blood cell counts, blood cortisol and glucose levels) and genetic (expression of five genes involved in growth, immunity and metabolism) traits of Rohu. The experimental ammonia dose significantly affected the tested biological parameters (p < 0.05), causing moderate-to-severe gill tissue damage. In general, compared with those in the control group, 16%–25% slower growth, 12%–30% lower survival and 15%–56% higher O₂ consumption were observed for the treatment groups. Blood glucose and cortisol levels increased with increasing ammonia levels, but blood cell counts decreased. The five selected candidate genes showed a differential expression pattern in response to the ammonia dose, with higher expression in the control group and lower expression in the treatment groups. The results indicate that different concentrations of ammonia impose stress on different orders of magnitude in the experimental fishes. Therefore, it can be inferred that the presence of ammonia in aquatic/farming environments can adversely affect production performance; the severity of damage during production depends on the concentration of ammonia. Therefore, maintaining no or minimum ammonia levels in farming environments is urgently needed for sustainable aquaculture production of Rohu.