Patterns and Scaling of Reproductive Output in Paddlefish Polyodon spathula and Its Conservation Implications

Abstract

We used a large, three-state data set to investigate if larger female Paddlefish Polyodon spathula reproduce disproportionately more than smaller females. The approach was to assess the relation between fecundity F, expressed as raw egg weight, and fish weight W, in the expression F = aWb. We compared results among three fisheries for Paddlefish harvested in the three states and between two stocks and compared results between total fish weight and total raw egg weight with results across taxa presented in other studies. Paddlefish from all three state-managed fisheries (Montana, North Dakota, and Oklahoma) showed hyperallometric increases in fecundity, expressed as raw egg weight, with fish weight (i.e., b > 1). For Montana females, hyperallometry was greatest (b = 1.75; n = 8,487), followed by North Dakota (b = 1.61; n = 9,549) and Oklahoma (b = 1.47; n = 14,294). Paddlefish from Montana and North Dakota in general allocated a lower percentage of their total weight to egg weight (asymptotic gonadosomatic index [GSI∞]) than did Oklahoma Paddlefish (Montana: 21.46%; North Dakota: 20.01%; and Oklahoma: 24.22%). The hyperallometric increases in raw egg weight with fish weight reported here depict only one of several conservation benefits associated with maintaining larger and older fish in the populations. Conclusions about weight–fecundity relationships for a particular species should be considered with an adequate understanding of the complete life history and factors which would affect somatic growth versus fecundity tradeoffs.