Age, Growth, and Reproduction of the sandpaper skate, Bathyraja kincaidii

Skates (Rajiformes) are exploited for food worldwide, comprising as much as 55% of the annual elasmobranch catch (Compagno 1990). Skates, like most elasmobranches, are susceptible to over-exploitation due to their life history characteristics of slow growth and late maturation. Two once abundant species of skates, the barndoor skate (Raja laevis) and the Irish Sea skate (Raja batis), have been fished to only fractions of their historical population sizes (Brander 1981, Casey and Myers 1998). Therefore it is important to determine age and size at maturity for commercially important and bycatch species. These characteristics are important to fisheries managers for stock assessments that aid in management decisions.

Bathyraja kincaidii is a common bycatch species in trawls off of central California (NMFS trawl survey data, 2002), however no life history information is known for this species. Therefore, the purpose of this study is to characterize some aspects of the life history for Bathyraja kincaidii. The objectives of this study are to: 1) determine an appropriate technique for clarifying growth zones on both vertebral centra and caudal thorns, 2) compare age estimates of vertebral centra to caudal thorns, 3) validate these age estimates using centrum edge characteristics, 4) relate these size-at-age estimates to reproductive status to determine age at first maturity 5) and apply these age estimations and their corresponding sizes to an appropriate growth function to describe growth characteristics.