Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8658
Title: Seasonal physiological dynamics of maturing female southern flounder (Paralichthys lethostigma)
Author: Casey A. Grieshaber, Stephen R. Midway, Frederick S. Scharf, Heather Koopman, J. Adam Luckenbach, Mollie A. Middleton
Publication Year: 2016
Journal: Conservation Physiology
Volume: 4
Issue: 1
Pages: cow043
DOI: doi:10.1093/conphys/cow043
Keywords: reproductive physiology,steroids,lipids,maturation,southern flounder

Physiological information is rarely used in descriptions of maturity for managed, wild fish species; however, the use of physiological data holds great promise to provide important detail on the complexities of oocyte development and maturity. Investigating southern flounder (Paralichthys lethostigma)—an overfished commercial and recreational fishery resource—we examined pre-spawn physiological changes in females to provide further detail of the maturation process. Given that adults of this species complete maturation and spawn in unknown offshore locations, information on pre-spawn physiological changes is particularly informative for both size- and age-based patterns of maturity. We evaluated seasonal and ontogenetic changes in hormone concentrations in blood plasma that are commonly associated with sexual maturation, in addition to quantifying and classifying lipid stored in liver tissue. We found a strong positive relationship between body weight and lipid content during all months, as well as evidence for mobilization of lipids among larger females in September and October, presumably for gonadal development. Throughout the sampling period, the lipid content of smaller individuals was dominated by structural lipids (as opposed to storage lipids). In contrast, larger individuals possessed greater amounts of storage lipids. This suggests that larger, putatively maturing individuals were accumulating storage lipids for later production of vitellogenin. Females sampled for blood sex steroids and ovarian histology showed different testosterone and estradiol concentrations between putatively maturing and immature fish, and temporal variation with peaks in October and November. Overall, emerging patterns of liver lipid content and composition and blood steroid concentrations describe a multi-month maturation process that is often managed one dimensionally over short time periods. Insights from this work will improve our understanding of the life history of southern flounder, with the potential for better understanding of the dynamics of offshore spawning migration and informing subsequent species management.

Theme: Sustainable, safe and secure seafood for healthy populations and vibrant communities
Foci: Provide scientific support for setting annual catch limits and measure results of annual catch limit implementation
Provide scientific support to ensure safe seafood for healthy populations and characterize how human activities and climate affect risks from pathogens, chemical contaminants and biotoxins