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

Biology

Life Cycle and Reproduction

The biology of the rougheye rockfish species pair remains poorly known. The longevity of species in the pair exceeds that for most other Sebastes species, with a maximum age recorded anywhere of 205 years for a specimen from southern Alaska (Munk 2001). Adults reach a maximum length of approximately 90 cm. Length-at-age boxplots (Figure 8) reveal similarsize-at-age for males and females. Length-at-age data show considerable variability around fitted von Bertalanffy models, and there is a dearth of information for the younger age classes (Figure 9). Although large natural variations occur in lengths-at-age, age readings of otoliths are generally precise, as are length measurements.


Figure 8: Boxplots of Length-at-age by Sex for Rougheye Rockfish Species Pair

Figure 8: Boxplots of length-at-age by sex for rougheye rockfish species pair.

Symbols indicate mean age, horizontal marks indicate the 2.5% and 97.5% quantiles, and whiskers show the extent of the data. Number of observations per box are indicated along the top. Source: Haigh et al. (2005). 


Figure 9: Length-at-age Relationship for Rougheye Rockfish Species Pair Fitted using Von Bertalanffy Growth Equation:
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Figure 9: Length-at-age relationship for rougheye rockfish species pair fitted using von Bertalanffy growth equation.

Source: Haigh et al. (2005).


Figure 10: Bubble Plot Representing Observed Age Proportions in Various Years for Rougheye Rockfish Species Pair in PMFC 5E (WQCI)

Figure10: Bubble plot representing observed age proportions in various years for rougheye rockfish species pair in PMFC 5E (WQCI).

Background shading indicates the one year where data come from research surveys, and the remainder come from the commercial fishery. Diagonal lines give reference years for cohort progression. Numbers below the horizontal line at age 0 show the number of fish aged each year. Age 60 represents a plus-class.  Source: Haigh et al. (2005).


Figure 11: Catch-curve Analysis to Estimate Total Mortality (Z) for (a-b) 1997 Survey Data (n = 431), (c-d) 1996 Commercial Data (n = 301), and (e-f) 2003 Commercial Data (n = 415)

Figure 11: Catch-curve analysis to estimate total mortality for 1997 survey data, 1996 commercial data, and 2003 commercial data.

(a,c,e) p = proportions-at-age, both observed (vertical bars) and predicted (solid curves) from Schnute and Haigh’s (2006) catch-curve model. The recruitment anomalies assumed are highlighted as dark vertical bars. Full selectivity is assumed by age 40. (b,d,f) Posterior samples of Z as histograms. Solid vertical lines indicate the mode from the model fits. Dashed vertical lines indicate the mean Z-values, dotted vertical lines indicate the 2.5% and 97.5% quantiles. Source: Haigh et al. (2005).

Approximately half of all males are mature at 400-450 mm, females at close to 470 mm. Females are approximately 20 years old at 50% maturity (McDermott 1994). The principal spawning period off BC is in April. Like all viviparous Sebastes species, fertilized eggs remain within the ovary until larval extrusion and may obtain at least some of their nutrition from the female parent during development (DFO1999). Sebastes larvae occur near the surface where they feed opportunistically on invertebrate eggs, copepods, and euphausiids; juveniles occur at midwater depths where they feed on larger prey items (Moser and Boehlert 1991). Planktonic larvae of Sebastes can be found up to 500 km offshore from the BC coast, far from adult habitat; however, their midwater residency (200-250 m) as juveniles subjects them to shoreward geostrophic advection (Moser and Boehlert 1991). Currently, there is no evidence to show that larvae and juveniles of rougheye rockfishes follow patterns different from those of other Sebastes species.

The generation time using the formula tgen = k + 1/M , where K = 20 (age at 50% maturity) and M = 0.035 (natural mortality rate, McDermott 1994), is 48 years.


Predation

In the Gulf of Alaska, rougheye rockfishes consume primarily shrimp (Pandalus borealis, P. montagui tridens, hippolytids, and crangonids), composing roughly 45-60% by weight of total stomach contents (Yang and Nelson 2000). They also consume fish species, including walleye pollock (Theragra chalcogramma), Pacific herring (Clupea pallasi), eulachon (Thaleichthys pacificus), Pacific sand lance (Ammodytes hexapterus), myctophids, zoarcids, cottids, snailfish, and flatfish. In the Gulf of Alaska, fish make up roughly 15-20% of total stomach contents (Yang and Nelson 2000). Additional food items include Tanner crab (Chionoecetes bairdi), cephalopods, amphipods, mysids, euphausiids, cumaceans, isopods, and polychaetes. While all size-classes of rougheye rockfishes primarily consume shrimp, fish less than 30 cm have a higher proportion of amphipods in their diet whereas fish larger than 30 cm consume more fish. Krieger and Ito (1999) note that rougheye rockfishes will leave the bottom to capture various prey species.


Interspecific Interactions

Rougheye rockfishes co-occur with numerous commercially harvested species (Figure 12), including arrowtooth flounder Atheresthes stomias and Pacific ocean perch Sebastes alutus. Other than competition for food resources with these species, there is no current information on interactions that might limit the survival of rougheye rockfishes.


Physiology

Unknown


Figure 12: Abundance of the Top 20 Species in Trawl Tows (1996-2004) that Captured at Least One Rougheye Rockfish in the Preferred Depth Range (170-650 m)

Figure 12: Abundance of the top 20 species in trawl tows (1996-2004) that captured at least one rougheye rockfish in the preferred depth range (170-650 m).

Abundance is expressed as a percent of total weight of all species caught in the tows. Source: Haigh et al. (2005).


Dispersal/Migration

No information exists for this species pair on the dispersal patterns during the planktonic phase or on the migration patterns of the adults. Like other Sebastes species, dispersal of planktonic larvae is probably influenced by ocean circulation patterns. Gharrett et al. (2005) infer that spatial movement is limited based on the apparent genetic heterogeneity among various geographic populations.


Adaptability

Unknown. Susceptible to barotrauma.