Research Document - 2000/119

Acoustic surveys of Smith Sound, Trinity Bay, 1995-2000

By G.A. Rose

Abstract

A dense spawning aggregation of cod was first observed in Smith Sound, Trinity Bay in the spring of 1995. Since that time several acoustic surveys have been attempted. The original survey results have been reworked here to conform with revised analytical protocols comparable to those used in present surveys. The first 1995 survey indicated the presence of approximately 9.5 million adult cod, primarily of year-classes 1990, 1989, and 1988. A survey in the spring of 1998 indicated the presence of approximately 7 million adult cod primarily of the 1990 and 1992 year-classes. A survey in January 1999 indicated the presence of approximately 11.5 million fish with high proportions of the 1995, 1994, and 1992 year-classes. Relatively strong recruitment from the 1995 spawning suggests a difference between the recruitment patterns in offshore (where the 1994 year-class dominates) and Smith Sound. Surveys in June 1999 indicated the presence of less than 1 million adult cod, and it is thought that these surveys occurred toward the end of spawning in 1999, and that most cod had already left the Sound. Surveys in January 2000 found a large abundance of cod of ages 2-15 (ca. 11-12 million fish in total). These fish were segregated by size and maturity within the Sound and comprised a total mean biomass of ca. 22,000 t (mean of 2 surveys). The 1990 and 1992 year classes were present in relatively large numbers and the year-classes of 95, 96, and 97 were also relatively well represented.

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