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

Distribution

Global Range

Rougheye rockfish, Sebastes aleutianus (Jordan and Evermann 1898) are reported to range from north of Japan, through to the Kamchatka Peninsula, the Bering Sea, the Aleutian Islands, the Gulf of Alaska, and the west coast of North America from British Columbia (BC) to southern California (Figure 4). Although range extends into Asian waters, records from the northwestern Pacific are poorly documented (Froese and Pauly 2005).


Figure 4: North American Distribution of Rougheye Rockfish Species Pair

Figure 4: North American distribution of rougheye rockfish species pair.

Distribution adjacent to Asian countries is not well documented (Froese and Pauly 2005).


Canadian Range

Figure 5 shows the areal extent of rougheye rockfish, Sebastes aleutianus (Jordan and Evermann 1898) as inferred from commercial groundfish trawl and longline catch rates for fisheries that target this entity at depths ranging from 0 to 800 m over the period 1996 through 2004. Choice of grid cell size influences the estimation of occupied area – cell size often shows a positive correlation with inferred area of occurrence. This effect is aggravated by sparse and infrequent tow locations represented by a single point. In reality, fishing events (trawl tows and longline sets) traverse tens of kilometres, often following contours and looping back on themselves. Given this scenario, a 5 km x 5 km cell gives a reasonable approximation of a typical fishing event. At this grid cell size, the known habitat or “area of occupancy” covers at least 35 000 km2. Table 1 offers a similar summary from commercial and survey logs from the trawl fishery where the estimated area of occupancy covers approximately 30 000 km2 between 0 and 800 m. Due to the extent of trawl and longline sets mentioned above, the former estimate is preferred. Depth distributions from commercial data indicate that 95% of rougheye rockfish, Sebastes aleutianus (Jordan and Evermann, 1898) caught occurred between 170 and 650 m (Figure 6). Figure 7 shows all available bathymetry bounded by these depths (blue shading), giving a rough estimate of the “extent of occurrence” of 37 000 km2.


Figure 5: Mean CPUE (kg/h) of rougheye rockfish species pair in 25 km2 grid cells along the BC coast

Figure 5: Mean CPUE (kg/h) of rougheye rockfish species pair in 25 km2 grid cells along the BC coast.

The shaded cells give an approximation of the area of occupancy (35 100 km2) as determined using groundfish trawl tow and longline set data collected between 0 and 800 m from 1996 to 2005 inclusive. Source: Haigh et al. (2005).

 

Table 1: Bathymetric Determination of Total Available and Observed Occupied Areas by 100-m Depth Interval for Rougheye Rockfishes
Depth Interval
(m)
Total Area
(km2)
Occupied Area
(km2)
Percent
Occupied
1-10046 0892 9086.3
101-20036 4328 90524.4
201-30016 4687 83647.6
301-4007 2763 90553.7
401-5002 7661 95170.5
501-6001 7821 33274.7
601-7001 5611 30583.6
701-8001 4131 16782.6
Total:115 03430 23226.3

Based on events from commercial fishing and research surveys located in 25 km2 grid cells overlaid on a 1 km2 ocean depth grid. Source: Haigh et al. (2005).