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Research Document - 2001/129

A phase '0' review of Elasmobranch biology, fisheries, assessment and management

By A.J. Benson, G.A. McFarlane and J.R. King


Elasmobranch catches in British Columbia (BC) averaged 550t in the 1970s and 1980s and increased to a maximum of 1850t in 1997. The average catch between 1998 and 2000 was 1400t. This trend mirrors the global elasmobranch catches that have risen steadily from an average of 200 000t in the 1940s to over 800 000t in recent years. The increased catches reflect the growing interest in directed elasmobranch fisheries that is the result of emerging markets. Fisheries and Oceans Canada (DFO) acknowledges the need for a scientifically defensible approach to the development of new fisheries. A phased approach that is based on the precautionary principle is applied to these fisheries. The available information at each step is utilized for fine tuning management strategies and research needs. There are three steps in the process, designated as Phases 0, 1, and 2. This report is a Phase 0 study that is intended to address questions raised by managers and that will form the basis for subsequent research and management actions. The questions asked are:

  1. What is known about the biology and productivity of skates and sharks that are caught in BC waters and/or other jurisdictions?
  2. What is known about the biomass and stock size structure of BC skates and sharks and how does this relate to historical stock conditions?
  3. What are the appropriate harvest levels, given the biology and status of skates and sharks?
  4. What information is available on the bycatch and associated mortalities, of skates and sharks in other fisheries?

There are three species of ray, ten species of skate, and fourteen sharks that are present in BC waters, but only big skate (Raja binoculata), longnose skate (Raja rhina), black skate (Bathyraja interrupta), and sixgill shark (Hexanchus griseus) are regularly taken as bycatch in BC fisheries. Of these, big skate is the most important, and represents 70% of the total sorted elasmobranch catch over the past 4 years. The majority of the catches are taken in Hecate Strait. A review of the biology of elasmobranchs is presented and indicates that the largest species are the most vulnerable to exploitation. Based on this, big skate is probably the least resilient B.C. species.

Research needs that must be addressed for improved assessment and management are: determination of the number and geographical limits of BC elasmobranch populations, the development of aging methods for these species, and obtaining accurate life history parameters for BC elasmobranch species. It is recommended that managers take action to ensure recruitment, and to improve catch statistics. Management recommendations include: species-specific size limits, sorting and accurate reporting of catches from all fisheries, and capping skate catches at the median level of the past four years.

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