Submitted to: Book of Abstracts World Aquaculture Society
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2014
Publication Date: 2/19/2015
Citation: Mcentire, M.E., Riche, M.A., Beck, B.H., Carter, D. 2015. Effect of contrasting agents on survival, performance, and condition of larval hybrid striped bass Morone chrysops x M. saxatilis in tanks [abstract]. Book of Abstracts World Aquaculture Society. p. 311.
Interpretive Summary: Adding the right amount of clay (Kaolin) or algae to the water to create turbidity (cloudiness) improves fry survival and growth, because hybrid striped bass fry are cannibalistic. The turbid water prevents the fish from seeing each other and also makes their live feed (zooplankton) standout. By adding algae paste at 350 – 583 algae cells/mL to tank water results in the optimum survival. The use of kaolin clay worked about as well as the algae paste at less than one fortieth the costs. By looking at various ratios of fry length and how uniform the ratios are among fry within the tank, some conclusions could be made about the cannibalistic interactions that are occurring among fry in the tank. Therefore these ratios could be used to predict and reduce future losses that could be expected during grow-out of the fry, or to determine the frequency of grading (removal the largest fry from the tank) that is necessary to reduce cannibalism. Increasing turbidity appears to allow the fry grow more uniformly in length and size along with improving survival.
Technical Abstract: Turbidity is important in the tank culture of larval cannibalistic fish. The principal goal of these studies were to characterize the utility and feasibility of select contrasting agents, either algae or inert soil, at improving sunshine bass survival and uniformity of size at time of weaning to an artificial diet. The two concurrent experiments evaluated the impact of algal density, i.e. greenwater, or the impact of dispersed kaolin relative to greenwater or clearwater on hybrid striped bass fry performance. Four day post hatch (dph) larvae were cultured on L-type rotifers, micro-cyst and regular cyst Artemia with their respective tank water treatments applied once daily. Prior to feeding on 19 dph (experiment 1) or 21 dph (experiment 2), sub-samples of fish (n > or = 70 per tank) were photographed under a dissecting scope for morphometric analysis. The fish were measured for standard, fork, tail, and total length along with body depth (immediately posterior to the swimbladder). On day 20 dph (experiment 1) or 22 dph (experiment 2), fish in each tank were bulk weighed to the nearest 0.1 mg and four sub-samples collected, weighed, and enumerated to determine average fish weight per tank as well as survival. The optimum tested range of greenwater culture for hybrid striped bass using algae paste once daily was between 629 - 1127 mg/m3 (350 - 583 cell/mL). Dispersed kaolin worked as well as greenwater culture. Using contrasting agents improved fish length, condition, tail length ratio (TLR), and uniformity of the fish at the time of weaning onto prepared diets. Increasing turbidity appears to skew fish length and TLR toward larger values. Tail length ratio shows promise as an early indicator of cannibalism. Increasing turbidity appears to decrease the size advantage of the largest fish in the tank, which allows the smallest fish to catch-up.