Master of Science (M.S.)
Moss Landing Marine Laboratories
Age and growth characteristics of the roughtail skate Bathyraja trachura, a poorly-known deep-water species, were determined from samples collected along the continental slope of the contiguous western United States. A new maximum size was established at 91 cm TL. Age was estimated using a traditional structure (vertebral thin sections) and an alternative non-lethal structure (caudal thorns). Based on poor precision and significantly lower age estimates when compared to age estimates from thin sections, caudal thorns were determined not to be a useful ageing structure for this species. Age estimates from vertebral thin sections were used to model growth. Annual band deposition was found to be a reasonable assumption for this species, but was not validated. Assuming annual band deposition and using length-at-age data, the best model for describing growth of B. trachura was the two parameter VBGF, (Lâˆž = 101.25, k = 0.09). Although females grew slower and reached a larger maximum size than males, their growth parameters were not statistically different therefore data were pooled (ARSS; p = 0.78). The maximum age determined for B. trachura was 20 yrs for males and 17 yrs for females using vertebral thin sections. First and 50% maturity occurred in males at 58.0 cm TL (~11 yrs) and 72.0 cm TL (~14 yrs). First and 50% maturity occurred in females at 58.0 cm TL (~7 yrs) and 77.0 cm TL (~ 13yrs). Gonosomatic and hepatosomatic indices did not indicate a seasonal trend of the reproductive cycle, suggesting that reproduction may be year round.
Davis, ChanteÌ, "Age, growth, and reproduction of the Roughtail Skate Bathyraja trachura (Gilbert, 1892) from the eastern North Pacific" (2006). Capstone Projects and Theses. 83.