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COSEWIC assessment and status report on the Bocaccio in Canada

Habitat

Habitat Requirements

Larval bocaccio have been caught up to 480 km from the California coast. Young of the year may reside in the upper water column for a few months; most settle to the bottom by the age of 3-4 months (Love et al. 2002). Young bocaccio generally inhabit shallower depths than the adults and often form schools (Eschmeyer et al. 1983). Young bocaccio have been captured in gillnets in nearshore sub-tidal depths off the west coast of Vancouver Island (Gillespie et al. 1993). Off southern California, juveniles are generally captured in depths of 30-120 m, occasionally to 200 m, and may be associated with kelp beds (Moser 1967).

Adult bocaccio are found over a variety of substrates in California, including rocky reefs and open bottom (Eschmeyer et al. 1983). In B.C., the maximum recorded depth of capture in the commercial fishery is greater than 800 m (Fig. 8), but these few data probably represent mistakes in depth recording or species identification by observers. Most specimens are captured in depths of 60-340 m during bottom trawling, while midwater trawl catches tend to occur over bottom depths of 60-200 m. Their presence in midwater trawl catches and salmon troll catches indicate they can be semi-pelagic in behaviour (A. Amos, F. Crabbe, R.N. Best, R.A. Best, pers. comm. Appendix 1).


Figure 8: Distribution of Bocaccio Catches by 20-m Depth Interval for Bottom and Midwater Trawling

Figure 8: Distribution of bocaccio catches by 20-m depth interval for bottom and midwater trawling.

The vertical lines at 77m and 309m demark the depth zone where 95% of all sets that captured bocaccio were conducted (January 1996-June 2001).


Figure 9: Species Composition Ranked by Weight of Catch in All Bottom and Midwater Trawl Tows that Captured Bocaccio (January 1996-June 2001)

Figure 9: Species composition ranked by weight of catch in all bottom and midwater trawl tows that captured bocaccio (January 1996-June 2001).

Bocaccio cohabit with a wide variety of groundfish species (Fig. 9). Catches in midwater trawling occur while targeting on yellowtail (Sebastes flavidus) and widow rockfish (S. entomelas). They are observed less frequently in the more extensive midwater trawl fishery for Pacific hake (Merluccius productus), which tends to occur over deeper waters or off the edge of the continental shelf.


Area of Habitat

From Figure 8, we note that 95% of the bottom trawl landings come from tows conducted in bottom depths of 77-309 m. If we assume that this depth stratum reflects “preferred” habitat for bocaccio, and that the available habitat extends for the entire outer B.C. coast, then a simple expansion indicates that the area of available habitat exceeds 48 000 km2 (Fig. 10). This excludes semi-enclosed waters and inlets known to be adult habitat, as well as the shallower nearshore waters, which are known habitat for juveniles (Gillespie et al. 1993).


Figure 10: Projected Habitat Area for Adult Bocaccio Based on Preferred Bottom Depth Zone of 77-309 m

Figure 10: Projected habitat area for adult bocaccio based on preferred bottom depth zone of 77-309 m.

Shaded area equals 48 346 km2. Note that the shaded area excludes enclosed waters and inlets, some of which have proven to be habitat for adult and young bocaccio, and shallower coastal waters, which may be habitat for juveniles.


Trends

There is no information on trends in the amount of habitat available to bocaccio. The widespread distribution of bocaccio on the outer coast and in Hecate Strait implies that the coastwide population is not at risk from loss of habitat. Possible impacts of habitat loss or environmental change in enclosed waters such as the Strait of Georgia are unknown.


Protection/Ownership

The widespread distribution of bocaccio over the continental shelf implies that protection/ownership issues do not currently threaten this population.