Radiometric age validation and spatial distribution of the Antarctic Toothfish, (Dissostichus mawsoni) : implications for a deep-sea Antarctic fishery

• Main Author: Brooks, Cassandra M
• Format: Text
• Language: unknown
• Published: Digital Commons @ CSUMB 2008
• Subjects: Antarctic Toothfish; Dissostichus mawsoni; Southern Ocean; age validation; lead-radium dating; habitat mapping; deep-sea fisheries; Antarctic fisheries; Antarctica; age estimation; Antarctic; Austral; Ross Sea; The Antarctic; Antarc*
• Online Access: https://digitalcommons.csumb.edu/caps_thes/74; https://digitalcommons.csumb.edu/cgi/viewcontent.cgi?article=1073&context=caps_thes

Antarctic toothfish (Dissostichus mawsoni) are subject to an increasingly important commercial fishery in the Southern Ocean, yet their life history characteristics and population structure remain largely unknown. In this study, Antarctic toothfish otoliths were obtained from American long-line fishing vessels in the Ross Sea, Antarctica. Age estimates obtained by counting annual growth increments in otolith sections indicate Antarctic toothfish live to at least 39 years of age. Lead-radium dating was used to validate ages up to 27.3 (range 21.7 -34.1) and provided support for ages up to 39 years of age using the methodology applied in this study. Validation also provided support for VBGF parameters, which indicate toothfish grow relatively slowly (k = 0.111; L∞ = 158.9; t₀ = -0.605). Fish ages were then superimposed on a habitat map of the Ross Sea, Antarctica and broken into discrete spatial areas. Differences in age data within these areas was tested using ANOVA. There was a relationship between fish age and maturity increasing with depth; younger, less mature fish were more often found on the shallower continental shelf and older fish were more often found in the deeper regions on the continental slope. However, there was far more variability than expected and other oceanographic and ecological factors likely effect age structure distribution significantly. Older and most mature individuals were found on ridges in the northern Ross Sea, consistent with the hypothesis of an austral summer spawning migration. An effective management strategy might focus on protecting the northern ridge habitat to potentially maintain long-term viability of Antarctic toothfish populations. Additionally, Antarctic toothfish vital rates should be considered before expanding the Ross Sea fishery.