Research Document - 2005/082

Spawning stock biomass reference points for spring and fall spawning herring in the southern Gulf of St. Lawrence

By Chouinard, G.A., G.A. Poirier, and C. LeBlanc

Abstract

Spawning stock biomass reference points consistent with the Precautionary Approach were derived for the spring and fall spawning components of southern Gulf of St. Lawrence herring. The two reference points are the Limit Reference Point (LRP) and the Upper Stock Reference (USR). Below the level of spawning biomass corresponding to the LRP, removals from the stock should be kept to the lowest possible while between the LRP and the USR, the removal rate should be lower than the removal rate reference. Above the USR, the removal rate should not exceed the removal rate reference. Stock and recruitment data for the two components were fitted to Beverton-Holt and Ricker stock-recruit models to determine if the two models can be used to identify the LRP. However, the model fits were poor. Given high recruit per spawning biomass ratios when the two components recovered, appropriate LRPs for the two components were calculated as the average of the 4 lowest biomass estimates, which occurred about the late 1970’s and early 1980’s. LRPs for the spring and fall components were 22,000 t and 51,000 t, respectively. To determine the USR, expected spawning stock biomass assuming average recruitment (age 2) and the removal rate reference (F0.1; 0.35 for the spring component and 0.32 for the fall component) were calculated using spawner per recruit analyses. Interim values for the USR for the spring and fall components were 54,000 t and 172,000 t, respectively.

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