Effects of different dietary oils on egg quality and reproductive performance in rainbow trout Oncorhynchus mykiss

A Pretty Kettle of Fish: A Review on the Current Challenges in Mediterranean Teleost Reproduction

The Mediterranean region is facing several environmental changes and pollution issues. Teleosts are particularly sensitive to these challenges due to their intricate reproductive biology and reliance on specific environmental cues for successful reproduction. Wild populations struggle with the triad of climate change, environmental contamination, and overfishing, which can deeply affect reproductive success and population dynamics. In farmed species, abiotic factors affecting reproduction are easier to control, whereas finding alternatives to conventional diets for farmed teleosts is crucial for enhancing broodstock health, reproductive success, and the sustainability of the aquaculture sector. Addressing these challenges involves ongoing research into formulating specialized diets, optimizing feeding strategies, and developing alternative and sustainable feed ingredients. To achieve a deeper comprehension of these challenges, studies employing model species have emerged as pivotal tools. These models offer advantages in understanding reproductive mechanisms due to their well-defined physiology, genetic tractability, and ease of manipulation. Yet, while providing invaluable insights, their applicability to diverse species remains constrained by inherent variations across taxa and oversimplification of complex environmental interactions, thus limiting the extrapolation of the scientific findings. Bridging these gaps necessitates multidisciplinary approaches, emphasizing conservation efforts for wild species and tailored nutritional strategies for aquaculture, thereby fostering sustainable teleost reproduction in the Mediterranean.

The effect of temperature and dietary energy content on female maturation and egg nutritional content in Atlantic salmon

The environment experienced by a female influences reproductive traits in many species of fish. Environmental factors such as temperature and diet are not only important mediators of female maturation and reproduction but also of egg traits and offspring fitness through maternal provisioning. In this study, we use 3-year-old tank-reared Atlantic salmon from two Finnish populations to investigate the effect of temperature and diet on maturation and egg traits. We show that a temperature difference of 2°C is sufficient to delay maturation in female Atlantic salmon whereas a 22% reduction in dietary energy content had no effect on maturation. Diet did not influence the body size, condition or fecundity of the mature females or the size or protein content of the eggs. However, a higher energy diet increased egg lipid content. Neither female body size nor condition were associated with egg size or fat/protein composition. Our results indicate that female salmon that have a poorer diet in terms of energy content may have a reproductive disadvantage due to the lower energy provisioning of eggs. This disadvantage has the potential to translate into fitness consequences for their offspring.

Enhancing Reproductive Performance of Freshwater Finfish Species through Dietary Lipids

Dietary lipid manipulation in the feed of commercially cultured finfish is used not only to improve production and culture but also to enhance their reproductive performances. The inclusion of lipid in broodstock diet positively affects growth, immunological responses, gonadogenesis, and larval survival. In this review, existing literature on the importance of freshwater finfish species to aquaculture and the inclusion of dietary lipid compounds in freshwater fish feed to accelerate the reproduction rate is being summarized and discussed. Although lipid compounds have been confirmed to improve reproductive performance, only a few members of the most economically important species have reaped benefits from quantitative and qualitative lipid studies. There is a knowledge gap on the effective inclusion and utilization of dietary lipids on gonad maturation, fecundity, fertilization, egg morphology, hatching rate, and consequently, larval quality contributing to the survival and good performance of freshwater fish culture. This review provides a baseline for potential future research for optimizing dietary lipid inclusion in freshwater broodstock diets.

Lipid metabolic disorders and physiological stress caused by a high-fat diet have lipid source-dependent effects in juvenile black seabream Acanthopagrus schlegelii

This study was conducted to evaluate the effects of different dietary lipid sources on growth performance, lipid metabolism, and physiological stress responses including oxidative stress (OS) and endoplasmic reticulum stress (ERS) of juvenile Acanthopagrus schlegelii (initial weight 0.88 ± 0.01 g) fed a high-fat diet (HFD). Four isonitrogenous and isolipidic experimental diets containing different lipid sources were formulated: fish oil (FO), palm oil (PO), linseed oil (LO), and soybean oil (SO), respectively. Results indicated that fish fed HFD supplemented with FO significantly improved growth than SO treatment. The high concentrations of aspartate aminotransferase and alanine transaminase were found in HFD supplemented with SO. Fish fed dietary LO supplementation showed significantly lower serum cholesterol, triglyceride, low-density lipoprotein, and high-density lipoprotein contents than those in SO group. Likewise, hepatic paraffin section analysis indicated that HFD with PO or SO supplementation increased fat drop. The expression levels of peroxisome proliferators-activated receptor alpha (pparα) and silent regulator 1 (sirt1) were significantly elevated by HFD with FO or LO supplementation. Additionally, the key marker of OS malonaldehyde was significantly increased in FO and SO groups. ERS-related genes were activated in dietary PO or SO supplementation and, hence, triggering inflammation and apoptosis by promoting the expression levels of nuclear factor kappa B (nf-κb) and c-Jun N-terminal kinase (jnk). Overall, the present study reveals that lipid metabolic disorders and physiological stress caused by a HFD have significant lipid source-dependent effects, which have important guiding significance for the use of HFD in marine fish.