In 2004, 68% of total production of fish, crustaceans and mollusks (termed seafood, coming from fresh, brackish and salt water) came from capture fisheries and the remaining 32% from aquaculture. Today, aquaculture supplies over half of the world’s total seafood production, and as the fastest growing animal food production sector is poised to supply two-thirds of global seafood production by the year 2030. Our decreased reliance on capture fisheries is due in part to over-harvesting of stocks but has also been impacted by climate variability that results in changes in fish supply. In turn, our reliance on aquaculture has increased and is projected to continue to grow as the demand for seafood increases and climate change continues to impact aquatic ecosystems.
Much of the growth in aquaculture has and will continue to come from intensification of production systems, which may increase the strains placed on animals in these systems. Intensification can result in increased stress associated with increased handling, increased stocking densities and deterioration of water quality, diverting energy away from growth and development and potentially making them more sensitive to additional stressors or disease. Overlay the increasing challenges from climate change, particularly warming of aquatic environments and persistent drought, and scenarios emerge where the development of new aquaculture practices to increase efficiency are directly intertwined and related to the capacity of the animals to cope with climate change. To mitigate future impacts of climate change on aquaculture, there is a need to increase the efficiency of aquaculture production systems while preserving the stress tolerance or resilience of aquaculture species to changing environmental factors.
Carrying on from decades of foundational research on sturgeon physiology and hatchery technology of cultured sturgeon by Dr. Serge Doroshov in the Department of Animal Science at UC Davis, we are developing research in our group that will focus on understanding the interactive effects of hatchery-associated stressors and climate change stressors on the physiological performance and disease resistance of white sturgeon across developmental stages.
One mechanism of increasing productivity in aquaculture is through the production of triploid fish. Triploids contain an extra set of chromosomes, which typically results in sterility. Sterile fish have the potential to reallocate energy from reproductive growth to somatic growth, resulting in increased growth and production rates. White sturgeon are unique compared to many other species of fishes, in that triploids are actually fertile and are, therefore, still potentially useful in caviar production. However, there is still much to be learned about triploid fish physiology, especially with the increasing amount of evidence that suggests triploids underperform in suboptimal conditions (i.e. low oxygen and high temperature environments) compared to diploids. Our research aims at understanding if and how diploid and triploid white sturgeon differ in their stress, metabolic, and immunological physiology under different environmental conditions.
Cannibalism, the behavior of eating flesh of the same species, is common in many fishes. The rate of cannibalism often increases in aquaculture settings because of high fish densities, stressful abiotic factors, and no options for escape. The aquaculture industry has traditionally sought to reduce cannibalism as much as possible in order to maximize yield. However, cannibals are significantly larger than non-cannibals and may have other physiological advantages. If cannibals do indeed exhibit greater performance than their non-cannibal siblings, there may be interest in rearing cannibals at hatcheries. We are currently focusing on this idea in burbot, Lota lota, an important species for food production and conservation. Our primary goal is to determine if there is a genetic basis for cannibalism by identifying differences in gene expression between cannibal and non-cannibal juvenile burbot. We are also examining indices of physiological performance (e.g. resting metabolic rate, critical thermal maximum) to determine if there are whole-body physiological differences between the two feeding strategies.
Fiske, A.J*, Van Enenennaam, J.P., Todgham, A.E., Young, S.P., Holem-Bell, C.E., Goodbla, A.M., and Schreier, A.D. 2019. A comparison of methods for determining ploidy in white sturgeon (Acipenser transmontanus). Aquaculture.
Leal, M.J.*, Van Eenennaam, J.P., Schreier, A.D., and Todgham, A.E. 2019. Triploidy in white sturgeon (Acipenser transmontanus): Effects of acute stress and warm acclimation on physiological performance. Comp. Biochem. Physiol. A. 229:10-17.
Leal, M.J.*, Clark, B.E.#, Van Eenennaam, J., Schreier, A.D., and Todgham, A.E. 2018. The effects of warm temperature acclimation on constitutive stress, immunity, and metabolism in white sturgeon (Acipenser transmontanus) of different ploidies. J. Comp. Biochem. Physiol. A. 224:23-34.