Increasing global rates of diminished fertility in males has been suggested to be associated with exposure to environmental contaminants (ECs). The aquatic environments are the final repository of ECs. As the reproductive system is conserved in vertebrates, studies on the effects of ECs on fertility endpoints in fishes provide us with valuable information to establish biomarkers in risk assessment of ECs, and to understand the ECs-related fertility threat. The aim of the present review was to evaluate associations between ECs and fertility determinants to better understand ECs-related male fertility threat in male fishes. Wildlife studies show that the reproductive system has been affected in fishes sampled from the polluted aquatic environment. The laboratory studies show the potency of ECs including natural and synthetic hormones, alkylphenols, bisphenols, plasticizers, pesticides, pharmaceutical, alkylating, and organotin agents to affect fertility determinants, resulting in diminished fertility at environmentally relevant concentrations. Both wildlife and laboratory studies reveal that ECs adverse effects on male fertility are associated with a decrease in sperm production, damage to sperm morphology, alternations in sperm genome, and decrease in sperm motility kinetics. The efficiency of ECs to affect sperm quality and male fertility highly depends on the concentration of the contaminants and the duration of exposure. Our review highlights that the number of contaminants examined over fertility tests are much lower than the number of contaminants detected in our environment. The ECs effects on fertility are largely unknown when fishes are exposed to the contaminants at early developmental stages. The review suggests the urgent need to examine ECs effects on male fertility when a fish is exposed at different developmental stages in a single or combination protocol. The ECs effects on the sperm genome are largely unknown to understand ECs-related inheritance of reproductive disorders transmitted to the progeny. To elucidate modes of action of ECs on sperm motility, it is needed to study functional morphology of the motility apparatus and to investigate ECs-disrupted motility signaling.

The aim of this study was to investigate changes in reproductive success including fertilization and hatching rates and larval performance as indicated by body weight and resistance to osmotic stress in captive common barbel (Barbus barbus L.) throughout the reproductive season. Spawning of B. barbus broodstock in captivity proceeded from February 01 to June 21 during 2006. Within the spawning period, fertilization and hatching rates and larval performance (body weight and resistance to osmotic stress) were studied at 7-day intervals. The average number of spawnings for each female was 2.8. Average fecundity was 1650 ± 460 eggs per spawning. A high proportion of females delivered poor egg quality (overripe eggs) during the spawning season from 57% on February 15 to 38% on May 31. The lowest fertilization and hatching rates were observed at the beginning (February 1, 18.5 ± 2.5% and 5 ± 2.5%, respectively) and the end (June 21, 25 ± 7% and 5.5 ± 2.5%, respectively) of the spawning period. While the highest values of both rates were found in period from March 22 (72.5 ± 5%) to May 10 (68 ± 4%) and from April 19 (53.8 ± 10%) to May 17 (50.5 ± 5%), respectively. The lowest larval body weight and resistance to osmotic stress were found at the beginning (8.0 ± 0.7 mg and 0 ± 0%, respectively) and the end of the spawning period (8.0 ± 0.7 mg and 25.2 ± 5%, respectively). The highest larval body weight and resistance to osmotic stress were recorded from March 15 (11.3 ± 0.9 mg) to May 31 (11.0 ± 0.7 mg) and from May 10 (93.5 ± 5%) to May 31 (90.7 ± 8%), respectively.

A three-month research was conducted to evaluate the influence of supplementing a plant protein- (PP-) rich diet (60% of fish meal (FM) was replaced with a mixture of alternative PP sources) with selenium nanoparticles (Se-N) on sperm kinetics, fertilization capacity, and antioxidative responses in Arabian yellowfin sea bream (Acanthopagrus arabicus) males. In this point, graded levels of Se-N at 0, 0.5, 1, 2, and 4 mg/kg were added to the PP-rich diet. Also, a FM-based diet was used as a positive control. Two hundred and eighty-eight brooders (males: g and females: g; ) were randomly distributed into eighteen 10 m³ rectangular concrete tanks (8 males: 8 females in each tank), and every three tanks were fed with one of the experimental feeds for three months. The seawater temperature and salinity were 18-22°C and 40-41‰, respectively, during the husbandry period. Selenium retention increased in the liver, testes, and semen of males with increasing dietary Se-N level ( ). Sperm density in fish fed with 2 mg Se-N/kg PP-rich diet ( ) was higher than those fed control, 0, 0.5, and 1 mg Se-N/kg PP-rich diets. The percentages of sperm motility in 60 s and 300 s after activation, sperms with straight movement, the longevity of sperm motility, and fertilization rate increased with increasing Se-N level in the PP-rich diets ( ). The highest and lowest semen superoxide dismutase activities were in fish fed 4 and 2 mg Se-N/kg PP-rich diets, respectively. The highest glutathione peroxidase activity in semen was in fish fed 4 mg Se-N/kg PP-rich diet, and the lowest values were in fish fed 0 and 0.5 mg Se-N/kg PP-rich diets. Total antioxidant capacity values in semen of fish fed 1 and 4 mg Se-N/kg PP-rich diets were higher than the other treatments. Fish fed with PP-rich diet without any Se-N supplementation had higher malondialdehyde level in the semen compared to the other groups. Results showed that supplementing PP-rich diet with 2-4 mg Se-N/kg can improve sperm kinetics and enhance fertility potential in A. arabicus males.