2024/02/23 by Dennis L. Scarnecchia, Jason D. Schooley, Aaron Slominski +4 · 1 voice
Biochemistry, Genetics and Molecular Biology · Environmental Science · #Fish Ecology and Management Studies #Marine and fisheries research #Reproductive biology and impacts on aquatic species
paper · doi:10.1002/tafs.10459
openalex publication_date 2024/02/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/05/21
Abstract Objective We investigated if large Paddlefish Polyodon spathula invest in testis weight disproportionately more than smaller males, as expressed by the gonadosomatic index (GSI). The approach was to assess the relation between testis weight F (i.e., the combined weight of both testes) and fish weight W in the expression F = aWb. The hypothesis was that sperm competition in Paddlefish would be expected (with b > 1) based on observations of several male fish attending a female spawner in a past study in the Osage River, Missouri. Methods We used a large, three-state data set from three fisheries (Montana, North Dakota, and Oklahoma) to evaluate isometry and allometry in the power function relationship between fish weight and testis weight. Result All three data sets showed hyperallometric increases in testis weight with fish weight (i.e., b > 1). For Montana males, hyperallometry was greatest (b = 1.56; n = 8798), followed by North Dakota (b = 1.36; n = 8209) and Oklahoma (b = 1.22; n = 9571). Paddlefish from Montana and North Dakota had much lower testis weights through age 18 and much lower fish weights through age 25 than Oklahoma Paddlefish. By ages 17–25, mean male GSI in Oklahoma declined, whereas it remained level at about 1.5 for combined Montana and North Dakota Paddlefish. Throughout their lives, at each age, Montana and North Dakota Paddlefish allocated a higher percentage of their total weight to testis weight and reached a higher asymptotic GSI (GSI∞) than did Oklahoma Paddlefish; GSI∞ was 1.50 for Montana fish, 1.44 for North Dakota fish, and 1.26 for Oklahoma fish. Conclusion Results provide evidence supporting the occurrence sperm competition (i.e., b > 1), as would occur when two or more males compete to fertilize the eggs of a female spawning Paddlefish. Comparisons among species and stocks are made but were limited by an acute shortage of data on male testis weights and other testis characteristics (e.g., sperm size, energy content), and reproductive investment in Paddlefish and most other fishes in other localities.