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COSEWIC Assessment and Status Report on the Rougheye Rockfish sp. type I and sp. type II in Canada

Habitat

Habitat Requirements

Krieger and Ito (1999) used manned submersibles to determine the habitat preferences of rougheye rockfishes and shortraker rockfish (S. borealis). Their observations revealed that greatest densities occurred on bottoms with soft substrates, in areas with frequent boulders, and on slopes greater than 20°. The association with soft substrate may be attributable to preferred prey items like pandalid shrimps (stomach content analyses, Yang and Nelson 2000). Krieger and Ito (1999) speculated that boulders might act as territorial markers, current deflectors, or structures to enhance prey capture. Their data also indicated that rougheye rockfishes avoid flat bottoms. Regardless of speculation on why this species pair adopts these habitat preferences, the observations suggest that rougheye rockfish habitat may be relatively unfavourable for trawling methods.


Figure 6: Histogram of Depth-of-capture for Rougheye Rockfish Species Pair as Reported in Commercial Trawl Log Books (1996-2005)

Figure 6: Histogram of depth-of-capture for rougheye rockfish species pair as reported in commercial trawl log books (1996-2005).

The vertical lines denote the 2.5% and 97.5% quantiles that are used to infer the preferred depth range for the species pair and to determine the maximum potential shelf-wide habitat range and distribution (see Figure 7). The distribution of all trawl sets is shown in light grey bars.


Figure 7: Estimated Range and Distribution of Habitat of Rougheye Rockfish Species Pair in Canadian Waters (based on preferred depth distribution of 170 m to 657 m -- see Figure 6)

Figure 7: Estimated range and distribution of habitat of rougheye rockfish species pair in Canadian waters, based on preferred depth distribution of 170 m to 657 m.

The maximum potential habitat based on depth preference is 37 145 km2 (blue shading). The estimated occupied habitat based on trawl logs only (5x5 km grid) is 18 530 km2 (green shading), or 49.9% of the potential habitat. Source: Haigh et al. (2005).


Habitat Trends

Not applicable.


Habitat Protection/Ownership

Although no official habitat protection exists, fisheries management controls removals of this species pair through coastwide quotas that are administered through an individual-vessel-quota system. The preferred bottom types of rougheye rockfishes – steep-slope, boulder habitats (Krieger and Ito 1999) – act as potential deterrents to fishing, at least from bottom trawling. Longline gear can presumably access these sites. The depth preference of this species limits its exposure to recreational harvest.