Aquaculture, Fish and Fisheries最新文献

In this brief report, we report on the occurrence of young-of-the-year common carp, as well as older juveniles, in a golf course irrigation pond in Stockholm County, Sweden (59°16′40.4″N 18°28′0.6″E). This documents a case of natural reproduction of the regularly stocked non-native carp in Swedish waters, near the northern limit for the stocking operations. Stocking of common carp in Sweden is generally conducted under assumptions that reproduction is not possible due to low spring-time water temperatures not meeting the reproductive requirements of common carp. Our observation suggests that risks for ecological impacts through the establishment of self-reproducing populations of common carp can be higher than previously assumed. We recommend that this observation is considered when deciding on permits for future carp stocking in Sweden.

The fisheries sector is a cornerstone of Bangladesh's economy, contributing significantly to national gross domestic product (GDP) and export earnings. However, the production of other marine fish falls short of national expectations due to various reasons, such as overexploitation, destruction of habitat, pollution, climate change and increasing pressure of poor fishers. This study examines the relationships between marine fish production, and climatic and oceanographic variables along the Cox's Bazar coast in the Bay of Bengal (BoB). Utilizing marine fish production data collected from fish landing centre, and satellite remote sensing data, the study evaluates the relationship between marine fish landing of five different groups and climatic and oceanographic variables. Multiple linear regression (MLR) models were employed to assess these relationships flowing into key analytical steps. The analysis revealed that certain climatic and oceanographic variables, including monthly average precipitation (LnPrecep), relative humidity (LnRhdt), sea surface temperature (LnSST), chlorophyll-A concentration (LnChl), salinity (LnSalinity) and dissolved oxygen (LnDo), have a combined explanatory power of 30.7, 46.10, 30.7, 40.4 and 24.0%, respectively, for the observed variability in monthly landing of five groups of marine fishes (hilsa, chanda, mackerel, rita and mixed) at Bangladesh Fisheries Development Corporation (BFDC)'s fish landing centre of Cox's Bazar. Additionally, these factors explain 38.8% of the variability in the total monthly landing of these five kinds of fishes combined. All the models were found to be statistically significant (p < 0.05). However, the relatively low R² values indicate other unaccounted factors, such as human pressure, particularly the increasing fishing pressure exerted by poor fishers contributing to reduction of marine fish production. These results highlight the relationships of climatic and oceanographic variables, and the volume of fish landings, or marine fish production, in the BoB, emphasizing the need for further research that includes growing fishing pressure to support sustainable marine fisheries management.

Lake Jipe, a shared resource at the Kenya-Tanzania border, has experienced significant fish introductions impacting its fish diversity. Despite these changes, the variations in morphometric characters of fish in the lake have not been documented following the establishment of non-native Oreochromis species. To address this, the present study assessed the morphological differences in Oreochromis niloticus, Oreochromis jipe and Oreochromis esculentus in Lake Jipe using morphometric traits to improve species identification for ease of fisheries management and conservation of the lake. These three species are known to share overlapping traits which makes their differentiation challenging. Using Image Analysis in ImageJ software version 1.54i and statistical analysis using R Version 4.3, the study hypothesized there were no significant differences in the morphometric characteristics of Oreochromis species in the lake. Welch's ANOVA revealed statistically significant correlations (p < 0.05) consistent in all species, with standard length and dorsal having the highest degree of significant positive association with total length, r > 0.8 across species. Correlations were weaker between total length and traits like caudal length (CL) and head length (HL), r < 0.5. All species exhibited negative allometric growth pattern (b < 3) suggesting faster growth in length than weight. This has important implications for fisheries management by guiding size-based harvesting strategies for sustainability. PCA revealed two principal components, (PC1 = 75.8%, PC2 = 10.4%) which contributed significantly to the observed variance in TL with TW. This study discriminated the species with total body weight and total length being the most distinctive morphometric measurements. Cluster dendrograms displayed site-specific species grouping with mixed groupings in the dendrograms indicative of potential hybridization events, especially where species distribution overlaps. This underscores the importance of further research to confirm species identity and potential admixture using genetic analyses. By refining the distinguishing traits, this study contributes to improved monitoring and management of Oreochromis fish populations in Lake Jipe.

Lindholm-Lehto PC, Pylkkö P. Aqua. Fish & Fisheries. 2024;4:e2200. https://doi.org/10.1002/aff2.200

In the caption of Figure 1 (on page 4 of 22) ‘arctic char (Salvelinus alpinus)’ was incorrect. It should be ‘brown trout (Salmo trutta)’.

We apologise for this error.

Global warming is upsetting for aquatic species, and probiotic treatment may help to diminish its impacts. In order to counter the negative consequences of elevated temperature on growth and well-being, rearing water of rohu (Labeo rohita) was supplemented with multispecies probiotics (1.0 mL/L). For 6 weeks, fingerlings weighing 10.08 ± 0.13 g were raised in triplicate at normal temperature (30°C) and higher temperatures (33°C and 36°C) with or without probiotics. Fish treated without probiotics showed substantial decreases in weight gain (WG) and specific growth rate (SGR) at 36°C in contrast to normal temperature (30°C). However, fish reared with probiotics showed enhanced WG and SGR at the highest temperature (36°C) compared to fish maintained without probiotics. In the group of fish supplemented with probiotics under high-temperature conditions, haemoglobin levels increased while glucose levels decreased. The number of irregularities in cells and nuclei of erythrocytes was dramatically reduced in probiotic-treated fish at 36°C. The relative mRNA level of three growth-relevant genes (growth hormone, gh, in the pituitary; insulin-like growth factor 1 and 2, igf-1 and igf-2, in the liver) decreased with increasing temperature but rose after probiotic addition. Fish at 36°C revealed a notable upregulation regarding the expression of genes for stress-associated heat shock protein 70 and 90 (hsp70 and hsp90), whereas their expressions were lowered following probiotics administration. Considering as a whole, the addition of probiotics to water improved blood biochemistry and cellular structure of blood and increased the expression levels of GH and IGF which consequently relieved growth retardation and stress in rohu.

Climbing perch, Anabas testudineus, were fed four diets: D0, D500, D1000 and D1500, containing 0, 500, 1000 and 1500 mg of vitamin C per kg of basal diet, respectively, over 70 days. After the growth trial, significantly higher final weight, percent body weight (%WG) and specific growth rate (SGR) were observed in fish fed D1000 followed by D500 and D0 diets. However, D1500 diet-fed fish had a significantly lower growth performance among all diet groups. The best feed conversion ratio and protein efficiency ratio were observed in fish fed D1000, followed by D500, with no significant difference between D0 and D1500 groups. Blood parameters were significantly influenced by vitamin C dosages. Fish fed on the D1000 diet exhibited significantly higher white blood cell (WBC), monocyte (MONO) and granulocyte (GRA) counts among all dietary groups. Vitamin C supplementation significantly increased platelet count in the D1000 group. Haemoglobin, haematocrit and red blood cell (RBC) counts showed an increasing trend with higher vitamin C levels, with the highest values in fish fed D1500 followed by D1000 diet. Total immunoglobulin (Ig) content was significantly higher in fish fed D1000 and D1500 diets compared to others, while peroxidase and catalase activity remained unaffected by the vitamin C levels. Vitamin C supplementation enhanced the salinity stress tolerance of fish, with the highest lethal time of 50% mortality (LT50) observed in the D1000 group, while other groups showed intermediate values. The polynomial regression analysis of %WG, LT50, WBC and Ig revealed that the optimum vitamin C supplementation levels were 773.75, 866.67, 934.71 and 1062.5 mg/kg diet, respectively, for climbing perch; these values are also in line with most of the growth and health performance parameters of the fish.

This study investigated the effects of varying dietary protein levels on the performance of tilapia reared in biofloc culture system without solid management. Five experimental diets containing crude protein (CP) levels of 32, 28, 24, 20, and 16% were tested in a completely randomized design in triplicate. Tilapia fingerlings (mean initial weight of 40.82 ± 0.38 g) were randomly stocked in biofloc tanks (effective water volume of 300 L) at a stocking density of 65 fish m⁻³. After 13 weeks of feeding trial, significant differences were observed in final weight (g), daily growth (g day⁻¹), feed conversion ratio, and yield (kg m⁻³) (p < 0.05). Water quality parameters remained unaffected by dietary treatments (p > 0.5). Notably, fish fed with diets containing 32%, 28%, and 24% CP demonstrated similar growth performance. Based on weight gain, a linear response plateau model estimated the minimal dietary CP level of 24.5%. Dietary CP levels altered visceral index (p < 0.05), but not visceral fat index, hepatosomatic index, or spleen somatic index (p > 0.05). Similarly, dietary CP levels did not significantly affect the fish composition (p > 0.05) and the haematological parameters of the experimental fish (p > 0.05). These results suggest that dietary protein in a small-scale biofloc system can be reduced from 32% to 24.5% without compromising fish health. However, appropriate solid management in biofloc systems is recommended to ensure optimal growth of fish.

Black bullhead Ameiurus melas are an environmentally tolerant fish that are often the target of population-level management efforts due to overabundance and potential negative influences on sport fishes. Descriptions of black bullhead growth and life history have been limited in part due to challenges in age estimation. Pectoral fin spines have been validated as age estimation structures for other ictalurids, but not black bullhead. We evaluated the precision of black bullhead pectoral fin spine and whole otolith age estimates from a northern Wisconsin lake. Age bias of pectoral fin spines was evaluated relative to whole otoliths using age estimates from two readers. Age estimates from both structures were applied to produce von Bertalanffy growth models. Precision of both structures was similar for both readers (66% and 58% agreement, 89% and 87% within 1 year). Pectoral fin spine age estimates showed higher between-reader agreement (59%, 95% within 1 year, CV = 9.2) than whole otolith age estimates (45%, 91% within 1 year, CV = 15.1). Pectoral fin spines may underestimate age relative to whole otoliths, particularly in older fish. von Bertalanffy growth model parameters were similar using both structures. Our findings suggest pectoral fin spine and whole otolith age estimates provide utility for age estimation in black bullhead, but modified methods of otolith processing and known age fish are needed to evaluate the accuracy of each structure.

Selectivity is an important parameter used to identify the portion of a stock caught by a fishing gear. In principle, fisheries management aligns the length at which 50% of individuals are selected for ($�L_{50}$) with minimum landing sizes. Harvest slot limits (the implementation of minimum landing sizes alongside maximum landing sizes) are in place for ballan wrasse, a sequential hermaphrodite commercially exploited in northern Europe. The selectivity of fishing gears used has yet to be investigated for this fishery. Two fishing gears were dismantled into their selective apertures, and fall-through experiments were used to determine the selectivity of each aperture, alternative escape panels and alternative entrances. Binomial logistic models were fit to estimate the relationships between selectivity, fish length and condition factor for each aperture. Linear models were used to investigate the relationships between $�L_{50}$, escape panel width and entrance diameter. Both commercial fishing gears retained fish both smaller and larger than the size-based harvest slot limits. Empirical relationships were developed to estimate escape panel widths and entrance diameters to align the $�L_{50}$ with harvest slot limits. Fisheries managers may use these relationships to propose modifications to fishing gear that align their selectivity with harvest slot limits. However, it should be considered that these relationships were based on morphology and do not account for behaviour within the estimation of selectivity.

Soft-shell crab aquaculture practices emerged as a profitable livelihood option in the study area due to its lower vulnerability to changing climatic conditions and high demand in the international market. Therefore, this study aims to identify the current growth of soft-shell mud crab farming to develop strategies to cope with future challenges. Random sampling was applied to collect primary empirical data from different stakeholders of the crab sub-sector based on structured and semi-structured questionnaires. In addition, focus group discussions (FGDs) and key informant interviews (KII) were arranged to collect information from a wide range of expert people to cross-validate the obtained information during the interviews. The study results indicated that the southwest region of Bangladesh has more than 380 farms having 5.55 ± 0.42 million seed crabs in demand in each cycle which is entirely dependent on wild stock. However, the wild crab harvesting amount has declined from 10.35 ± 2.07 to 4.38 ± 0.83 kg/day/person which represented a highly positive relationship with the active percentage of plastic cages that reduced from 99.43 ± 2.12% to 67.04 ± 4.75% during the investigated years. Farm mortality of stocking crabs has also increased by more than 8% in the last 9 years due to a lack of quality seed crabs. The soft-shell crab farmers preferred small stocking sizes to get quick moulting, ranging from 30.35 ± 2.59 to 43.50 ± 3.59 g. Most of the crab farmers used only tilapia fish as feed items leading to the increase in unit price from BDT 30.30 ± 1.98 to BDT 80.00 ± 2.46. The feeding demand and cost also increased many folds over the years with an increase in farm numbers and feed prices. So, crab hatchery development and formulated feed supply are inevitable for the sustainable growth of this sector.