Research Document - 2004/060

Analytical assessment and risk analyses for the herring (Clupea harengus harengus L.) stocks on the west coast of Newfoundland (NAFO Division 4R) in 2002.

By Grégoire, F., Lefebvre, L, Lavers, J.

Abstract

Sequential Population Analyses (SPA) were realized in 2003 on the spring-spawning and fall-spawning stocks of herring (Clupea harengus harengus L.) of the west coast of Newfoundland (NAFO Division 4R). The results of these analyses revealed that the spawning biomass of the spring stock appears to have risen from 35,011 t in 1997 to 67,851 t in 2002, and to 58,921 t in 2003. This last value is greater than the minimum acceptable limit B_LIM of 37,834 t, but close to the buffer limit B_BUF of 57,468 t. Fishing mortality among the oldest individuals (age 8 and older) would have exceeded the F_0.1 threshold on a few occasions in the late 1960s and the early 1980s and almost continuously throughout the 1990s. For this same stock, the probabilities of exceeding F_0.1 in 2003 would be less than 50 % for catches of less than 11,000 t. For the fall-spawning herring stock, the spawning biomass appears to have fallen from 71,412 t in 1994 to 53,373 t in 2002 and to 48,481 t in 2003. This last value is slightly greater than the B_LIM value of 47,953 t, but lower than the B_BUF limit of 61,074 t. For this stock, the probabilities of exceeding F_0.1 in 2003 would be less than 50 % for catches of less than 11,600 t. Results of the SPA reveal also important impreciseness in the calculation of some parameters and the presence of a retrospective pattern denoting a tendency to underestimate the real abundance of these two stocks. Consequently, the results of the SPA must be used with caution, and greater uncertainty must be ascribed to the projections derived from the risk analyses. Therefore, we are recommending a gradual increase in the TAC which should not exceed 20,000 t in 2003.

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