LIVE BAIT TRADE AS A PATHWAY FOR THE INTRODUCTION OF NON-NATIVE SPECIES: THE FIRST RECORD OF Dilocarcinus pagei IN THE PARANAPANEMA RIVER BASIN

Brazil has one of the most significant diversity of freshwater fish in the world, and this drives trade and fishing tourism. Several species of sport fish have characteristics and behaviors that favor fishing tourism and its related activities. Live baits are widely used in fisheries across the country, and at the end of fisheries, is common that anglers may release the remaining bait in rivers, lakes or reservoirs. Here we report for the first time the crab Dilocarcinus pagei in the Paranapanema River basin, and list the freshwater species that were introduced similarly. During field samplings between 2012/2016, and 2018/2019, we captured 10 individuals of D. pagei. One female in the Rosana Reservoir; and two juveniles, one female and six males in the Taquaruçu Reservoir. The literature review revealed 16 species used as live bait, the crab D. pagei and 15 fish species. Gymnotiformes were the largest number of species used as live bait. The basins that had introduction cases were in the Upper Paraná, Iguaçu, and Paraíba do Sul Rivers. The Paraguay-Lower Paraná River was the system that contributed with nine species to the most invaded ecoregion in Brazil, the Upper Paraná River basin. Anglers and live bait farmers should be aware of the risks and consequences of these constant introduction actions (propagule pressure), not releasing baits. In addition, the live bait trade must be monitored and controlled to occur only with species in their original river basin.

Methylmercury bioaccumulation in sport fish and the relation to human exposure

A long-lasting contaminant, methylmercury (MeHg), builds up in human bodies over a lifetime. Regularly eating contaminated fish may accumulate mercury to an amount that raises health concerns, especially for children and babies. Methylmercury is found throughout the parts of the fish that are eaten; cleaning or cooking methods cannot effectively reduce mercury exposure. The main focus of this thesis concerns the fish contamination in Lake Ontario and to conserve health from eating contaminated sport fish. Although mercury (Hg) is tightly regulated, mercury levels in fish still gradually increase throughout their life spans. Through the field data provided by the Ontario Ministry of Environment (MOE), greater amounts of methylmercury are found in older fish and predatory fish that eat other fish as part of their diet. A bioenergetics computer program, called Generic Bioaccumulation Model (BGM) (Luk, 1996), simulating the bioaccumulation of Hg in fish was applied to provide a good estimation of mercury levels for different species. It is an excellent tool in predicting the trends and magnitude of mercury levels among six sport fish in Lake Ontario. In addition, an estimation of human mercury consumption from fish was also developed. In most of the fish species, there is minimal risk to humans when eating fish less than two times a week. The species Walleye (Stizostedion vitreum) and its quality and quantity are of greatest concern, since it exhibits the highest mercury level among the six sport fish species.

Methylmercury bioaccumulation in sport fish and the relation to human exposure

A long-lasting contaminant, methylmercury (MeHg), builds up in human bodies over a lifetime. Regularly eating contaminated fish may accumulate mercury to an amount that raises health concerns, especially for children and babies. Methylmercury is found throughout the parts of the fish that are eaten; cleaning or cooking methods cannot effectively reduce mercury exposure. The main focus of this thesis concerns the fish contamination in Lake Ontario and to conserve health from eating contaminated sport fish. Although mercury (Hg) is tightly regulated, mercury levels in fish still gradually increase throughout their life spans. Through the field data provided by the Ontario Ministry of Environment (MOE), greater amounts of methylmercury are found in older fish and predatory fish that eat other fish as part of their diet. A bioenergetics computer program, called Generic Bioaccumulation Model (BGM) (Luk, 1996), simulating the bioaccumulation of Hg in fish was applied to provide a good estimation of mercury levels for different species. It is an excellent tool in predicting the trends and magnitude of mercury levels among six sport fish in Lake Ontario. In addition, an estimation of human mercury consumption from fish was also developed. In most of the fish species, there is minimal risk to humans when eating fish less than two times a week. The species Walleye (Stizostedion vitreum) and its quality and quantity are of greatest concern, since it exhibits the highest mercury level among the six sport fish species.

Evidence Dorsal Spine Removal is Nonlethal and Unharmful for Largemouth Bass in Florida

Largemouth Bass Micropterus salmoides, Florida Bass M. floridanus, and their intergrade are socially and economically valuable sport fish. In the southeastern United States, it is customary to age black bass (Micropterus) spp. using sagittal otoliths which requires killing the fish. Presently, fisheries managers and black bass anglers show reluctance to sacrifice large individuals. Development of a nonlethal ageing technique would not only allay concerns of sacrificing large black bass, but it could offer a pathway for new research, management, and conservation. We excised dorsal spines III–V from Largemouth Bass in Florida varying from 30–57 cm total length to evaluate the effects of the procedure on survival over 35 days. No mortalities were observed for fish with excised dorsal spines, and experiment-wide survival was 0.94 (0.87–1.00; 95% confidence interval). No significant differences in survival, weight change, or incidence of external injuries were observed between control and excised fish. The areas of spine excision healed with no visible infection or inflammation at the conclusion of the experiment. Therefore, dorsal spine removal offers managers a nonlethal option for collecting ageing structures of adult Largemouth Bass in Florida, including large individuals, and this result likely extends to other Micropterus spp. as well.