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

COSEWIC Status Report
on the
Rougheye rockfish
Sebastes sp.

Sebastes sp. type I
Sebastes sp. type II

in Canada
2007

Species Information

Name and Classification

Rougheye rockfish, Sebastes aleutianus (Jordan and Evermann, 1898) (sébaste à oeil épineux) has been considered one of 102 known species of the rockfish genus Sebastes, 96 of which live in the north Pacific Ocean. The taxonomic names stem from the Greek sebastos (magnificent) and aleutianus (Aleutian Islands where the species was first reported; Love et al.. 2002). The name “rougheye” refers to a series of spines (numbering 2 to 10) along the lower rim of the eyes (Love et al.. 2002). In Canada’s Pacific waters, 36 species of rockfish have been captured.

During preparation of this status report, two sympatric but genetically distinct species within what was considered rougheye rockfish were identified (Gharrett et al.. 2005, Hawkins et al.. 2005). As well as differences in allozymes, mitochondrial DNA and microsatellite DNA, differences in frequencies of two parasites (Hawkins et al.. 2005), colouration (Gharrett et al.. 2006, Hawkins 2005) and meristic and morphological characteristics (Gharrett et al.. 2006) have been described.

The two genetically distinct species have been named differently by two research teams: type I and type II (Gharrett et al. 2005, 2006), and Sebastes aleutianus and Sebastes sp. cf aleutianus (Hawkins et al. 2005). Based on differences in colouration described in the two papers, type I of Gharrett et al.. (2005, 2006) appears to correspond with Sebastes sp. cf. aleutianus of Hawkins et al.. (2005).

In order to recognize the existence of two species, but to not prejudge results of a future taxonomic revision that will formally name them, this report will refer to Sebastes sp. type I, rougheye rockfish type I, corresponding to the type I of Gharrett et al. (2005, 2006), and Sebastes sp. type II, rougheye rockfish type II, corresponding to the type II of Gharrett et al.. (2005, 2006). Where reference to the described species rougheye rockfish, Sebastes aleutianus (Jordan and Evermann, 1898) is necessary, this report will refer to the rougheye rockfish species pair or will refer to the entity by its full common and Latin name.


Morphological Description

Rougheye rockfish, Sebastes aleutianus (Jordan and Evermann, 1898) are relatively large rockfish with a maximum length typically in the 80 to 100 cm range (Love et al. 2002). This species pair appears red (Figure 1) with dark or dusky blotches of pigment in the dorsal region (Mecklenburg et al.. 2002). A light red lateral line is conspicuous as it contrasts with the otherwise dark red body. All but the pectoral fins are usually marked with black margins.


Figure 1: Rougheye Rockfish, Sebastes aleutianus (Jordan and Evermann, 1898), Ink (Hart 1973) and Photo

Figure1: Rougheye rockfish, Sebastes aleutianus (Jordan and Evermann, 1898), ink (Hart 1973) and photo.

Phenotypic differences in colouration and presence or absence of suborbital spines were reported to exist between the two genetically distinct species (Hawkins et al.. 2005). Gharrett et al.. (2006) reported that the two genotypes could be distinguished by gill raker length and number and body depth; type II have slightly fewer and shorter gill rakers and deeper bodies than type I. Discriminant analysis of morphological characteristics accurately delineated the two species in >94% of cases (Gharrett et al.. 2006). Colouration may not be a reliable guide for separating the genotypes; most type II fish have light colouration, but type fish I may be either light or dark coloured, and the proportion of each colour form changes geographically (Gharrett et al.. 2006).

Types I and II of Gharrett et al.. (2005, 2006), although sympatric, exhibit different spatial preferences, at least according to the proportions of the two types captured in trawl hauls (Gharrett et al.. 2005). While both types occur throughout the north Pacific, type I predominates in the northeast Pacific and in deeper water (A.J. Gharrett1, pers. comm.). Hawkins et al.. (2005) also observed that their Sebastes sp cf aleutianus predominated in deeper water. 

Rougheye weight increases as a near cubic function of length (Figure 2) with little difference between males (β = 2.93) and females (β = 2.88). Parameter estimates for the pooled sexes (α = 2.81 x 10-5; β = 2.90) suffice for this species.


Genetic Description

Researchers cannot use conventional tagging studies to assess population structure as rougheye rockfish do not survive the barotrauma (i.e., physiological damage associated with change in pressure) when brought from depth to the surface.


Figure 2: Rougheye Rockfish Species Pair, Weight vs. Length Using a Lognormal Linear Model: logW = logα + βlogL .

Figure 2: Rougheye rockfish species pair, weight vs. length using a lognormal linear model: 7. Source: Haigh et al. (2005).

Source: Haigh et al.. (2005).

Early studies (Tsuyuki et al.. 1968; Seeb 1986; Hawkins et al.. 1997) reported two phenotypes and inferred genetic differences. Recent studies of rougheye in the Gulf of Alaska provide evidence of genetic differentiation among co-occurring (sympatric) rougheye rockfish, based on microsatellite and mitochondrial DNA markers and distributions of allozyme allele frequencies (Gharrett et al.. 2005, Hawkins et al.. 2005). Gharrett et al.. (2005) confirmed these differences in 698 rougheye rockfish specimens sampled along the Pacific Rim from the Oregon coast to the Aleutian Islands and Bering Sea. All three types of genetic marker revealed strong and concordant evidence that rougheye rockfish comprise two sympatric species.


Designatable Units

The two genetically distinct species identified by Gharrett et al.. (2005, 2006) and Hawkins et al. (2005) have been identified and characterized primarily on the basis of samples from the USA. Rougheye rockfish type I and rougheye rockfish type II both occur in Canadian waters, although type I reportedly predominates. The relatively few Canadian samples (n=39) were all collected just south of the Queen Charlotte Islands, and all consist of type I from deep water (Figure 3, Gharrett et al.. 2005), but this could simply reflect the small sample size. Considerably more sampling will be required to determine the prevalence and distribution of types I and II in Canadian waters.


Figure 3: Locations of Rougheye Rockfishes Surveyed for Mitochondrial DNA and Microsatellite Variation

Figure 3: Locations of rougheye rockfishes surveyed for mitochondrial DNA and microsatellite variation. Chart (A) shows the locations of type-I fish and (B) the locations of type-II fish (circles) and presumed hybrids (triangles).

Chart (A) shows the locations of type-I fish and (B) the locations of type-II fish (circles) and presumed hybrids (triangles). The numbers within the circles are the sample sizes from each location; each triangle represents a single fish. Locations represent all collections within a 50 km radius. Adapted from Gharrett et al.. 2005.

In Pacific waters under Canadian jurisdiction, fisheries management and all previous studies have assumed a single panmictic stock of rougheye rockfish, Sebastes aleutianus (Jordan and Evermann, 1898). Because the two recently identified rougheye rockfish species have not been separated in past studies or in fisheries, for the purposes of this report it is assumed that rougheye rockfish type I and rougheye rockfish type II are covered equally well by the available information collected on the basis of a single species. A single designatable unit for each of rougheye rockfish type I and rougheye rockfish type II is assumed in Canadian waters, in the absence of information to the contrary.

Cryptic species of this kind increase the risk of loss of unrecognized genetic diversity, but there is no current information on status of each of the two putative species. Accordingly a single status report is considered to include the information for the two species.




Footnotes

1 Fisheries Division, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 1120 Glacier Highway, Juneau, AK 99801