Pacific Ocean Perch Sebastes Alutus Research Articles

Fishery and notes on the biology of Pacific ocean perch Sebastes alutus (Sebastidae) off the Commander Islands

The fishery and some aspects of the biology of the Pacific ocean perch Sebastes alutus off the Commander Islands. It has been established that the harvest of this species is episodic in nature, is not subject to seasonal dynamics and is carried out in a local area located west of the Bering Island. The contribution of this water area to the total catch of rockfishes in the Petropavlovsk-Commander subzone in 2001–2022 did not exceed 26.5%. Near the Commander Islands, S. alutus was observed at depths of 138–370 m at a water temperature near-bottom of 3.1–3.9°C, and in catches it was represented by individuals 17–45 cm length. Presumably the formation of accumulations in the upper part of the continental slope to the west of the Bering Island is due to the presence of an anticyclonic circulation, which contributes to the formation of high concentrations of zooplankton as the main food source and favorable conditions for the development of spawned larvae.

Cautious considerations for using multiple covariate distance sampling and seafloor terrain for improved estimates of rockfish density

Distance sampling is one of the most widely used methods for adjusting fish counts for detectability, which allows the estimation of absolute density. Further, abundance can be estimated spatially beyond the transect width with density surface models. The present study used a density surface modelling approach with survey data from line transects and terrain metrics from multibeam acoustic bathymetry data, integrated with a Geographic Information System, to estimate the population density of Pacific Ocean perchSebastes alutus(POP) within 6 sampling areas in the Gulf of Alaska (GOA) at 2 sampling scales: local and landscape. For adult POP, the final density model included depth as a significant predictor for density estimation at both the local and landscape scale. Additional factors included sponge coverage (local scale), aspect eastness and seafloor slope (landscape scale). Predicted densities of adult POP are highest on low (<5°) eastern-facing slopes with high sponge coverage (>75%), at depths of 100 to 200 m. By using habitat-based density models with data collected from line transect distance sampling and multibeam acoustic seafloor mapping surveys, we provide an alternative method for estimating rockfish abundance in untrawlable areas, which may help improve rockfish stock assessments and essential fish habitat descriptions and maps.

SOME DATA ON BIOLOGY AND DISTRIBUTION FOR LARVAE OF ROCKFISHES FROM GENUS SEBASTES IN THE WATERS OF THE AVACHINSKY BAY (KAMCHATKA PENINSULA)

Results of ichthyoplankton surveys conducted in the Avachinsky Bay in the springs of 2003–2018 are presented. The larvae of 3 species of genus Sebastes occurred in the bay, starting in March, as shortraker rockfish Sebastes borealis, pacific ocean perch Sebastes alutus, and rougheye rockfish Sebastes aleutianus. The maximal catches of the larvae were obtained at the depth ≤ 500 m, mostly over the deep-water canyons. Problems of the rockfish larvae identifying to species are discussed, as absence of the detailed identifier for these species. Photo-images of the larvae are presented for Sebastes alutus and Sebastes aleutianus collected in spring of 2018, their typical differences are considered. Size composition is presented for the larvae of Sebastes.

Long-term Bering Sea environmental variability revealed by a centennial-length biochronology of Pacific ocean perch Sebastes alutus

The productivity and functioning of Bering Sea marine ecosystems are tightly coupled to decadal-scale environmental variability, as exemplified by the profound changes in community composition that followed the 1976-1977 shift from a cool to a warm climate regime. Longer-term ecosystem dynamics, including the extent to which this regime shift was exceptional in the context of the past century, remain poorly described due to a lack of multi-decadal biological time series. To explore the impact of decadal regime shifts on higher trophic levels, we applied dendrochronology (tree-ring science) techniques to the otolith growth-increment widths of Pacific ocean perch Sebastes alutus (POP) collected from the continental slope of the eastern Bering Sea. After crossdating, 2 chronology development techniques were applied: (1) a regional curve standardization (RCS) approach designed to retain as much low-frequency variability as possible, and (2) an individual-detrending approach that maximized interannual synchrony among samples. Both chronologies spanned the years 1919-2006 and were significantly (p < 0.001) and positively correlated with sea surface temperature (March-December). The RCS chronology showed a transition from relatively slow to fast growth after 1976-1977. In both chronologies, the highest observed growth values immediately followed the regime shift, suggesting that this event had a critical and lasting impact on growth of POP. This growth pulse was, however, not shared by a previously published yellowfin sole Limanda aspera chronology (1969-2006) from the eastern Bering Sea shelf, indicating species- or site-specific responses. Ultimately, these chronologies provide a long-term perspective and underscore the susceptibility of fish growth to extreme low-frequency events.

Reproductive Biology of Pacific Ocean Perch and Northern Rockfish in the Aleutian Islands

AbstractEstimates of maturity (i.e., the proportion of mature individuals at age) play an important role in assessing stock productivity; however, this information has not been published for rockfishes in the Aleutian Islands. Ovary and otolith samples were collected from Pacific Ocean Perch Sebastes alutus and Northern Rockfish S. polyspinis during both fishery‐independent and fishery‐dependent cruises in 2010 to investigate maturity and other aspects of reproductive biology. Histological examination of ovaries indicated that both species exhibited general parturition in April, while specimens caught in the summer and fall were maturing and generally exhibited progressive stages of vitellogenesis. Histological analysis was more reliable when characterizing ovary condition than were macroscopic or visual assessments during the developing period. Estimates of natural mortality, based on a relationship with the gonadosomatic index, were 0.040 for Pacific Ocean Perch and 0.042 for Northern Rockfish. Mean fecundity estimates calculated for Northern Rockfish (89,320 oocytes) were correlated more with length and weight than age. Estimates of age and length at 50% maturity were 9.1 years at 32.4 cm for Pacific Ocean Perch and 7.6 years at 27.7 cm for Northern Rockfish and indicate maturation at younger ages than do previous studies from the Gulf of Alaska. This information on reproductive biology will improve estimation of fishing mortality reference points and management of these commercially important species in the Aleutian Islands.Received June 22, 2012; accepted December 10, 2012

Reproductive Biology of Pacific Ocean Perch in the Gulf of Alaska

AbstractDespite the ecological and economic importance of rockfish fisheries in Alaska waters, little information is available concerning the reproductive biology of the majority of federally managed rockfish species in the Gulf of Alaska. Pacific Ocean Perch Sebastes alutus are the most abundant and commercially important rockfish in this region. This study examines the reproductive biology of Pacific Ocean Perch within the Gulf of Alaska, utilizing histological techniques to microscopically examine ovarian tissue. Pacific Ocean Perch samples were obtained throughout the year during National Marine Fisheries Service and Alaska Department of Fish and Game scientific surveys, as well as scientific charters. Ovaries of Pacific Ocean Perch began to ripen during the month of August with yolk increasing until February. Embryos appeared within the ovaries during February and continued to grow and develop until parturition in May. Results from this study indicate the fork length at 50% maturity is 33.4 cm and the age at 50% maturity is 8.4 years. Both of these values are smaller than those currently utilized in the stock assessment of Gulf of Alaska Pacific Ocean Perch. Results from this study will improve the stock assessment of this species by providing more accurate estimates of reproductive parameters and reducing the uncertainty in estimates of length and age at maturity.Received July 30, 2012; accepted November 16, 2012

Defining spring transition: regional indices for the California Current System

While the physical and ecological importance of the spring transition in the California Current System (CCS) is well recognized, there is no widely agreed upon metric for tracking the phenomenon. Most metrics reflect oceanographic events of the northern CCS; few pertain to southern regions. Our goal was to compare 2 commonly used methods for identifying spring transition in the CCS that use data on wind-driven upwelling and coastal sea levels to 2 newly developed methods that use data on sea levels as well as satellite-derived sea-surface temperatures (SSTs). More specifically, we assessed whether methods typically used in northern regions of the CCS could be applied to other regions. To demonstrate the biological implications of those methods, we evaluated relationships between timing of spring transition and recruitment of 2 groundfish species, Pacific ocean perch Sebastes alutus and sablefish Anoplopoma fimbria. Our results suggest that while dramatic changes in wind-derived upwelling and coastal sea levels consistently indicate spring transition in the northern CCS, this is not the case for central and southern regions. In those regions, spring transition may be better represented by the rate of change in sea levels and/or changes in spatial patterns of SSTs. Only metrics based on wind-driven upwelling and sea levels were related to groundfish recruitment; when transitions in upwelling winds and sea levels were delayed, recruitment tended to be poor. We advise caution when identifying dates of spring transition and applying them to analyses of ecological phenomena; a combination of several methods may be required to reveal the multidimensional physical and biological changes that occur during that transition.

Assemblage Structure of Eastern Pacific Groundfishes on the U.S. Continental Slope in Relation to Physical and Environmental Variables

AbstractWe analyzed data from the National Marine Fisheries Service continental slope trawl surveys (1999–2002) to examine patterns in eastern Pacific groundfish assemblage structure in relation to longitude, latitude, depth, temperature, and interannual variation. The slope surveys spanned approximately 32–48°N and 200–1,200‐m depths. We focused on the 26 most abundant species, which made up more than 95% of the catch in terms of biomass. Assemblage structure was strongly correlated with depth and latitude. For the most part, changes in assemblage structure appeared to be fairly continuous, although there were more‐abrupt changes at approximately 500–600 m and in the vicinity of Point Conception and Cape Mendocino, California, and Cape Blanco, Oregon. There was also an interaction between depth and latitude; more northerly sites had deeper scores on the canonical axes than did more southerly sites of comparable depth. Shallower sites also showed more variation in assemblage structure with latitude than did deeper sites. We were able to identify five assemblages on the continental slope. Pacific grenadiers Coryphaenoides acrolepis, giant grenadiers Albatrossia pectoralis, deepsea soles Embassichthys bathybius, longspine thornyheads Sebastolobus altivelis, California slickheads Alepocephalus tenebrosus, and roughtail skate Bathyraja trachura formed a deepwater assemblage with a broad latitudinal range. Southern species that inhabited very shallow waters included splitnose rockfish Sebastes diploproa, spotted ratfish Hydrolagus colliei, English soles Parophrys vetulus, stripetail rockfish Sebastes saxicola, chilipeppers Sebastes goodei, and shortbelly rockfish Sebastes jordani. Shallow‐water, midlatitude species included spiny dogfish Squalus acanthias, longnose skate Raja rhina, Pacific hakes Merluccius productus, rex soles Glyptocephalus zachirus, bigfin eelpout Lycodes cortezianus, and sandpaper skate Bathyraja interrupta. Darkblotched rockfish Sebastes crameri, arrowtooth flounder Atheresthes stomias, and Pacific Ocean perch Sebastes alutus were identified as a shallow, northerly assemblage. The final group—sablefish Anoplopoma fimbria, brown cat sharks Apristurus brunneus, aurora rockfish Sebastes aurora, Dover soles Microstomus pacificus, and shortspine thornyheads Sebastolobus alascanus—occurred at different depths over a range of latitudes and might be best described as a shallow–middepth and midlatitude–southern grouping.

Rockfish (Scorpaenidae) Assemblages of Trawlable and Untrawlable Habitats off Vancouver Island, British Columbia

Abstract We compared assemblages of demersal rockfishes (Scorpaenidae) associated with two areas of the continental slope off northern Vancouver Island, British Columbia, Canada. Twenty and 21 sets of sunken gill nets were completed on trawlable and untrawlable areas, respectively. The species assemblages on the two areas were markedly different, as demonstrated by their diversity, evenness, and percent similarity and by cluster analysis. On the trawlable area, the catch was numerically dominated by Pacific ocean perch Sebastes alutus (37.6%), splitnose rockfish S. diploproa (23.5%), greenstriped rockfish S. elongatus (12.7%), and bocaccio S. paucispinis (7.3%). This contrasted with the untrawlable area, where the catch was numerically dominated by sharpchin rockfish S. zacentrus (70.8%), and redbanded rockfish S. babcocki made up half (14.5%) the remaining catch. We found no evidence to support the claim by some fishermen that exploited rockfishes on trawlable areas, especially Pacific ocean perch, are m...