Research Document - 2012/070

A risk-based decision-making framework for Buffalo River Inconnu (Stenodus leucichthys) that incorporates the Precautionary Approach

By A.C. Day, M. VanGerwen-Toyne, and R.F. Tallman

Abstract

Inconnu (Stenodus leucichthys) have been harvested as bycatch in the Great Slave Lake (GSL) commercial Lake Whitefish (Coregonus clupeaformis) fishery from 1945 to the present. The Buffalo River stock was heavily targeted at the mouth of this system in the springs of 1978 and 1979. The stock collapsed following this fishing pulse and has not recovered since. Inconnu become vulnerable to the fishery several years prior to maturity and are, therefore, vulnerable to recruitment overfishing. Using the precautionary approach (PA) framework, a PA model for management of GSL Buffalo River Inconnu was tabled at a regional advisory process organized by Fisheries and Oceans Canada (DFO) in Yellowknife, NT, on March 30 and 31, 2010. Catch-per-unit-effort of mature female Inconnu in experimental nets set at the mouth of the Buffalo River in spring between 1976 and 2008 was used as an index of spawning stock biomass (SSB) and biological reference points (BRP) of the PA model. Maximum removal rates were determined from examination of the response of population parameters of this stock to various rates of commercial harvest of Inconnu from the west basin of GSL. Upper and lower limit BRP SSBs were 10 and two mature female Inconnu caught per hour per net respectively. Recommended upper and lower limit removal rates were 40,000 kg and 10,000 kg respectively. Buffalo River Inconnu were assigned to the critical zone of the PA model and had a BRP SSB of 0.6 mature female Inconnu caught per hour per net for the last assessment done in 2008. Following the pulse fishing of 1978 and 1979, BRP SSBs have remained in the critical zone of the PA model, except in a single year. Levels of risk were assigned as moderate for the lower limit removal rate of 10,000 kg and high for all removal rates in excess of this amount. Given the critical status of Buffalo River Inconnu, a low level of risk can only be achieved through a closure of the fishery.

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