Fisheries & Aquatic Life

Dietary supplements attenuate the toxicity of heavy metals and enhance their elimination in fish

2026-04-16T11:45:21+02:00

Heavy metals cause a threat to the aquatic environment and to its inhabitants when their concentrations exceed safe limits. This applies to both metals considered priority substances (Pb, Cd, Hg) and trace elements that are necessary for life at appropriate doses (Cu, Zn, Fe, Co, Ni, Mn). They can cause toxic effects in fish due to their non-biodegradable properties and long persistence in the environment. A decrease in heavy metal concentration in organisms observed by various researchers after the use of feed supplements is a positive sign, pointing to the possibility of inhibiting the accumulation and toxic impact of these substances on tissues and organs. In this review article, we demonstrate that certain supplements (such as vitamins, boron compounds, melatonin, lysine, and probiotics), each acting through distinct mechanisms, can reduce the accumulation of heavy metals, significantly mitigate their toxicity in fish, and accelerate their elimination from fish tissues. Consequently, dietary supplementation may positively influence the production of fish intended for human consumption by preventing avoidable losses associated with the deterioration of fish health. Indirectly, it also protects consumers by reducing the risk of exposure to heavy metals that may be present in fish tissues.

Optimizing feeding strategies with dry diets to balance growth and reproductive quality in crucian carp (Carassius carassius) for conservation-oriented aquaculture

2026-04-16T11:45:26+02:00

Two commercial dry diets were fed to Carassius carassius (L.) juveniles for 60 days at 25°C, each at feeding intensities of 2.0%, 2.5%, or 3.0% of fish biomass per day, to determine the effects of feeding intensity on fish growth, condition factor K, incidence of body deformities, chemical body composition, and gonadal development. Growth of fish and K values were positively influenced by the feeding intensity; likewise fat content in fish bodies. In contrast, ash content was influenced negatively. Intensities of 2.5% and 3.0% resulted in high final incidence of body deformities (range 28.6-76.2%), whereas at 2.0% only 1.9-8.6% fish with deformities were recorded. Gonadal development increased with fish size and feeding intensity, with the most advanced reproductive stages in groups fed at 3.0% biomass/day. Feeding intensity exerted no negative effects on the histological structure of male and female germ cells. However, excessive feeding was associated with a reduced gonadosomatic index (GSI). Our results indicate that feeding at a level slightly below satiation (2.0-2.5% biomass/day) offers the best balance between fish growth, avoidance of body deformities and reproductive readiness. These findings provide guidance for the development of standardized protocols for aquaculture-assisted conservation of C. carassius, including stocking programs and captive breeding efforts.

The presence of vitamin D3 metabolic system in the ovary of Prussian carp (Carassius gibelio Bloch) – preliminary study on the potential role in the final oocyte maturation process

2026-04-16T11:45:32+02:00

This study aimed to immunolocalize vitamin D₃ (VD) metabolic enzymes (CYP27B1 and CYP24A1) and receptors (VDR and PDIA3) in the ovary of Prussian carp during the spawning season. Furthermore, the effect of VD on the final oocyte maturation measured as the percentage of germinal vesicle breakdown (GVBD) after 24 h of incubation, was investigated. We have shown, for the first time, the cytoplasmic CYP27B1, CYP24A1, and PDIA3 protein immunolocalization in the ovarian follicular cells. We have also confirmed the presence of VDR in the nuclei of follicular cells. Furthermore, we have shown the stimulating effect of VD on the final oocyte maturation in fish. Therefore, VD may contribute to the regulation of ovarian functions by activation of its receptors (VDR and/or PDIA3) and/or via the paracrine/autocrine action ensured by important metabolic enzymes, namely CYP27B1 and CYP24A1.

Light and scanning electron microscopy study of the olfactory organ of Milkfish, Chanos chanos

2026-04-16T11:45:36+02:00

This study investigates the ultrastructural and histological organization of the olfactory organ in milkfish (Chanos chanos). The olfactory rosette is fan-shaped and consists of 26-28 lamellae radiating from a central raphe located on the floor of the nasal chamber. Each lamella contains a connective tissue core covered by a two-layered epithelium composed of sensory and non-sensory regions. The sensory epithelium, located on the dorsal lamellar processes and the apical regions of the lamellae, contains three types of olfactory receptor neurons: ciliated, microvillous, and rod cells. The non-sensory epithelium, distributed along the basal, median, and outer regions of the lamellae, comprises mucous, chloride-like, lymphatic, basal, and supporting cells (both ciliated and non-ciliated). The stratified epithelial cells of the central raphe are densely packed and exhibit prominent microridges. The structural organization of the olfactory mucosa indicates a high degree of functional specialization associated with chemoreception in aquatic environments.

The effectiveness of alternative bait in blue swimming crab trap fishing – green mussel as the main ingredient

2026-04-16T11:45:40+02:00

Blue swimming crab (Portunus pelagicus) fishing in the Java Sea is mainly conducted using bottom gillnets, but traps are increasingly being used. Crabs caught in traps are generally larger, remain alive, and have fewer injuries, resulting in a higher selling price than those caught using gillnets. Trap fishing, however, requires suitable bait to be economically viable. The availability of commonly used natural bait, primarily ponyfish, is highly influenced by the season, and its fluctuating price is a major obstacle faced by fishers. This study evaluated the potential of alternative bait made from a mixture of green mussel and tapioca flour. The baits consisted of green mussel meat and tapioca flour at ratios of 2:1 (GM1) and 3:1 (GM2). Their effectiveness was compared with that of ponyfish bait (G0) in fishing trials conducted in September 2024 in Banten Bay over 20 days using 30 traps for each bait type. The difference in capture efficiency among bait types was not significant (p = 0.1581), although traps with ponyfish bait caught more crabs than those with alternative baits. However, crabs caught with GM2 bait were dominated by larger individuals than those caught with ponyfish bait. Our study suggests that alternative bait made from green mussel has the potential to substitute ponyfish bait in crab fishing. Green mussel is an easily obtainable and available year-round, with a low production cost, attractive aroma, durable texture, and relatively high effectiveness.

Feeding habits and some other biological aspects of Oreochromis niloticus (L.) and Cyprinus carpio (L.) in Lake Ardibo

2026-04-16T11:45:47+02:00

Ethiopian freshwater bodies support a substantial fishing population; however, their sustainable utilization has been limited due to the lack of comprehensive scientific information on the feeding ecology, reproductive biology, and length–weight relationships (LWRs) of commercially important fish species. This study investigated the feeding habits and selected biological characteristics of Oreochromis niloticus and Cyprinus carpio in Lake Ardibo from June 2022 to September 2023 based on monthly sampling campaigns. Fish specimens were collected using gillnets and hooks. Selected physicochemical parameters of the water, including temperature, pH, and dissolved oxygen, were measured and found to be within ranges suitable for fish survival. The LWRs of both species indicated nearly isometric growth patterns. The mean condition factor (K) was 1.77 for O. niloticus and 1.75 for C. carpio, with no significant differences between sexes (P > 0.05). Both species exhibited omnivorous feeding strategies, consuming a wide range of prey items. In O. niloticus, detritus occurred in 40% of the stomachs and contributed 41.38% of the total food volume, while Microcystis was present in 73.33% of the stomachs and accounted for 62.99% of the volume. In C. carpio, detritus and diatoms contributed 49% and 33.2% of the total food volume, respectively. Based on the Index of Food Preponderance (%IFP), detritus constituted 46.40% and 63.79% of the diet in O. niloticus and C. carpio, respectively. Ontogenetic analysis revealed an increase in the contribution of plant-origin diets with fish size in O. niloticus. Overall, the results indicate that both species adopt an omnivorous feeding strategy with a tendency toward detritivory and herbivory in larger individuals.