Genus Sebastes Research Articles

Sampling Efficiency of Longlines for Shortraker and Rougheye Rockfish Using Observations from a Manned Submersible

AbstractPopulations of demersal rockfish of the genus Sebastes are challenging to assess because they inhabit rocky areas that are difficult to sample with trawl gear. In contrast, longline gear can sample rocky areas, but several factors besides fish density can affect the relationship between catch rates and density. In this study, longline catch rates of shortraker rockfish Sebastes borealis and rougheye rockfish S. aleutianus were compared with observations of density from a manned submersible to evaluate the species’ catchability on longline gear. On separate occasions, rockfish behavior in the presence of longline gear was observed from the submersible. Densities averaged 3.0 shortraker and rougheye rockfish (combined) per 330 m2 of bottom (the effectively sampled area of a 100‐m transect). Longline catch rates averaged 2.7 shortraker and rougheye rockfish per skate of 45 hooks. Longline catch rates were not statistically affected by submersible observations. There was a positive trend between density and longline catch rates, but the relationship was not significant. As observed from the submersible, the proportion of fish free‐swimming near the longline increased through the duration of the set, indicating that rockfish were attracted to the line faster than they were caught. The catching process for shortraker and rougheye rockfish lasts longer than for more mobile species such as sablefish Anoplopoma fimbria.

Olfactory Receptor Related to Class A, Type 2 (V1r-Like Ora2) Genes Are Conserved between Distantly Related Rockfishes (Genus Sebastes)

V1r-like Ora genes express putative chemoreceptors that may function as pheromone receptors in fishes. We used a candidate gene approach to test whether V1r-like Ora2 genes show evidence of positive selection that could suggest a role in mate recognition and the avoidance of hybridization between closely related rockfishes. We amplified a 492-bp fragment of a single V1r-like Ora2 gene from each of 5 species of rockfish. Despite separation of up to 7.8 My, the sequence of V1r-like Ora2 is highly conserved. Genetic distances are small, and all our study species shared at least one sequence with another species. Sequence comparisons suggested that, although most amino acids were subject to purifying selection, 9 amino acids showed evidence of positive selection. Because many of these amino acids were not associated with the areas of the protein suggested to be involved in ligand binding based on structural similarity to other olfactory receptors, this signal may reflect an echo of the relaxation of selection associated with the speciation events that separate these species. Strong sequence conservation suggests that this gene is of functional significance. However, because of shared alleles among species, the V1r-like Ora2 gene, in isolation, would be unlikely to differentiate species during mating season.

Population structure of beaked redfish, Sebastes mentella: evidence of divergence associated with different habitats

Abstract Cadrin, S. X., Bernreuther, M., Daníelsdóttir, A. K., Hjörleifsson, E., Johansen, T., Kerr, L., Kristinsson, K., Mariani, S., Nedreaas, K., Pampoulie, C., Planque, B., Reinert, J., Saborido-Rey, F., Sigurðsson, T., and Stransky, C. 2010. Population structure of beaked redfish, Sebastes mentella: evidence of divergence associated with different habitats. – ICES Journal of Marine Science, 67: 1617–1630. Throughout their range, Sebastes spp. are adapted to a diversity of ecological niches, with overlapping spatial distributions of different species that have little or no morphological differences. Divergence of behavioural groups into depth-defined adult habitats has led to reproductive isolation, adaptive radiation, and speciation in the genus Sebastes. Recent genetic research, supported by life-history information, indicates four biological stocks of Sebastes mentella in the Irminger Sea and adjacent waters: a western stock, a deep-pelagic stock, a shallow-pelagic stock, and an Iceland slope stock. Congruent differences in fatty acids and parasites suggest that these genetically distinct populations are adapted to disparate trophic habitats in pelagic waters (shallower and deeper than the deep-scattering layer) and in demersal habitats on the continental slope. Morphology of pelagic forms is also more streamlined than demersal forms. Although genetic differences and evidence for reproductive isolation are clear, these populations appear to share common nursery habitats on the Greenland shelf. We propose a redefinition of practical management units near the Irminger Sea based on geographic proxies for biological stocks and minimizing mixed-stock catches according to the spatial patterns of the recent fishery.

Parallel amino acid replacements in the rhodopsins of the rockfishes (Sebastes spp.) associated with shifts in habitat depth

Among various groups of fishes, a shift in peak wavelength sensitivity has been correlated with changes in their photic environments. The genus Sebastes is a radiation of marine fish species that inhabit a wide range of depths from intertidal to over 600 m. We examined 32 species of Sebastes for evidence of adaptive amino acid substitution at the rhodopsin gene. Fourteen amino acid positions were variable among these species. Maximum likelihood analyses identify several of these to be targets of positive selection. None of these correspond to previously identified critical amino acid sites, yet they may in fact be functionally important. The occurrence of independent parallel changes at certain amino acid positions reinforces this idea. Reconstruction of habitat depths of ancestral nodes in the phylogeny suggests that shallow habitats have been colonized independently in different lineages. The evolution of rhodopsin appears to be associated with changes in depth, with accelerated evolution in lineages that have had large changes in depth.

DNA barcoding of Pacific Canada’s fishes

DNA barcoding—sequencing a standard region of the mitochondrial cytochrome c oxidase 1 gene (COI)—promises a rapid, accurate means of identifying animals to a species level. This study establishes that sequence variability in the barcode region permits discrimination of 98% of 201 fish species from the Canadian Pacific. The average sequence variation within species was 0.25%, while the average distance separating species within genera was 3.75%. The latter value was considerably lower than values reported in other studies, reflecting the dominance of the Canadian fauna by members of the young and highly diverse genus Sebastes. Although most sebastids possessed distinctive COI sequences, four species did not. As a partial offset to these cases, the barcode records indicated the presence of a new, broadly distributed species of Paraliparis and the possibility that Paraliparis pectoralis is actually a species pair. The present study shows that most fish species in Pacific Canadian waters correspond to a single, tightly cohesive array of barcode sequences that are distinct from those of any other species, but also highlights some taxonomic issues that need further investigation.

The Differential Response to Decompression in Three Species of Nearshore Pacific Rockfish

AbstractThe genus Sebastes (rockfishes) is an ecologically diverse group of fish, more than 60 species occurring off the Oregon, Washington, and California coasts. As of 2004, seven species of rockfish were classified as overfished by the Pacific Fishery Management Council. Because rockfishes often experience barotrauma to varying degrees when forced up from depth, the management of discard mortality has been difficult. In this study, the macroscopic, morphological, and physiological responses to decompression of black rockfish S. melanops, blue rockfish S. mystinus, and yellowtail rockfish S. flavidus, all nearshore species, were investigated. The rockfish were adjusted to 4.5 atmospheres absolute (ATA; 35 m) over a period of 7–10 d in hyperbaric pressure chambers and when neutrally buoyant were rapidly brought to surface pressure in a simulated ascent. They were then examined for barotrauma injury, and the heart ventricle, head kidney, liver, gill, and pseudobranch were collected for histological analysis. We observed more macroscopic barotrauma indicators in black rockfish and blue rockfish than in yellowtail rockfish. Histological analysis showed emphysema was present in the heart ventricle of more than one‐half of the black rockfish, 11% of the blue rockfish, and none of the yellowtail rockfish. No other tissue had observable injury at the histological level that was attributable to barotrauma. The lack of injury at the tissue level for black, blue, and yellowtail rockfishes decompressed from 4.5 ATA is remarkable.

Effects of simulated underwater vehicle lighting on fish behavior

Little is known regarding bias attributable to fish behavior for visual transects con- ducted using underwater vehicles (UVs). Experiments were conducted under 2 ambient illuminations to assess the behavioral responses of 7 north Pacific Ocean groundfish species to a light stimulus that simulated the approach of a UV. Species included sablefish Anoplopoma fimbria, Pacific halibut Hip- poglossus stenolepis, lingcod Ophiodon elongatus and 4 species in the genus Sebastes: blue rockfish S. mystinus, black rockfish S. melanops, copper rockfish S. caurinus and quillback rockfish S. maliger. Movement, as well as general activity, varied greatly between species. The most active spe- cies, sablefish, became agitated and moved away from the looming light source, while the least active species, Pacific halibut and lingcod, typically remained stationary. Of the 4 rockfish species, 2 demonstrated a strong response to ambient light level. Black rockfish and blue rockfish moved away from the looming light source, but avoidance was delayed under high ambient light. Bias probably differs among species, being greatest for those that are highly active and mobile, like sablefish. Fur- ther, ambient light may modulate bias, such that researchers need to be cautious about comparing results for surveys conducted at different depths and/or times of day.

Sounds of Captive Rockfishes

Abstract Sound production by many fish species has been studied extensively, but little is known about sound production by rockfishes (genus Sebastes), and only a few species have been reported to be soniferous. To determine if additional rockfish species produce sounds, passive acoustic recordings were made during 2007/08 at Hubbs-SeaWorld Research Institute and Southwest Fisheries Science Center in tanks containing Bocaccio (S. paucispinis), Cowcod (S. levis), Starry Rockfish (S. constellatus), and Sunset Rockfish (S. crocotulus). Data were collected using pre-amplified hydrophones (HTI-94-SSQ) and digitized at sample rates of 44,100 or 8,000 Hz (using an Edirol R-09 recorder or Edirol UA-5 sound card and Ishmael software, respectively). Three distinct sounds were recorded in tanks containing only S. paucispinis and two of those sounds occurred at different rates during light and dark conditions. Their common characteristics were low frequency (below 800 Hz), short duration (<4 s), and low source levels...

Rockfish ( Sebastes) that are evolutionarily isolated are also large, morphologically distinctive and vulnerable to overfishing

In an age of triage, we must prioritize species for conservation effort. Species more isolated on the tree of life are candidates for increased attention. The rockfish genus Sebastes is speciose (>100 spp.), morphologically and ecologically diverse and many species are heavily fished. We used a complete Sebastes phylogeny to calculate a measure of evolutionary isolation for each species and compared this to their morphology and imperilment. We found that evolutionarily isolated species in the northeast Pacific are both larger-bodied and, independent of body size, morphologically more distinctive. We examined extinction risk within rockfish using a compound measure of each species’ intrinsic vulnerability to overfishing and categorizing species as commercially fished or not. Evolutionarily isolated species in the northeast Pacific are more likely to be fished, and, due to their larger sizes and to life history traits such as long lifespan and slow maturation rate, they are also intrinsically more vulnerable to overfishing. Finally, the set of northeast Pacific species that are both fished and most intrinsically vulnerable to fishing are among the most evolutionarily distinctive. These findings suggest that, at least for this clade, extra attention should be paid to evolutionary distinctiveness when prioritizing species for conservation.

Bocaccio sounds in the Southern California Bight.

Sound production by many fish species has been studied extensively, but little is known about sound production by rockfishes (genus Sebastes), and only a few species have been reported to be soniferous. Passive acoustic recordings were made during 2007 and 2008 at Hubbs‐SeaWorld Research Institute and Southwest Fisheries Science Center tanks containing Bocaccio (S. paucispinis). Sounds in tanks were recorded using preamplified hydrophones (HTI‐94‐SSQ) and were digitized at sample rates of 44,100 or 8000 Hz. Recordings were collected at 14 locations in the Southern California Bight (SCB) using passive acoustic moorings, AURALs, sampling at 8000 Hz from August through October 2007. Three low frequency (<900 Hz), short duration (<4 s) sounds were recorded in tanks containing only Bocaccio multiple times. One of these sounds was also commonly recorded in the SCB and is the same sound that was recorded first by Thompson off San Clemente Island in the 1960s. This sound exhibited the same diel pattern as noted by Thompson, with maximum calling at night, peaking at dusk and dawn. This long‐term persistence of the same sound indicates that passive acoustic tools may be used for efficient monitoring of changes in rockfish populations over long time periods.

A multivariate stock–recruitment function for cohorts with sympatric subclasses: application to maternal effects in rockfish (genus Sebastes)

I present a multivariate stock–recruitment function (MSRF) for calculating recruitment when a cohort comprises sympatric subclasses. Sympatric subclasses emerge when there are closely interacting subgroups occupying a very similar niche, but whose ecology dictates distinct mortality rates. Examples include multispecies complexes of juvenile rockfish ( Sebastes spp.) in the California current and juvenile salmon ( Oncorhynchus spp.) in streams following different life history strategies. I derive an MSRF and apply it to the ecology of larval and juvenile rockfish with maternal effects. In several species of rockfish, older mothers produce superior larvae. This is called a maternal effect. For these species, larval and juvenile cohorts comprise several sympatric subclasses, each with a distinct mortality rate related to the age of their mothers. I apply this model to data for black rockfish ( Sebastes melanops ) in California and Oregon and find the recruitment estimates based on data from a declining population may overestimate productivity of a recovering population if maternal effects are neglected. The MSRF proves to be a flexible framework for studying recruitment in the presence of sympatric subclasses.

Structural complexity in relation to the habitat preferences, territoriality, and hatchery rearing of juvenile China rockfish (Sebastes nebulosus)

Conservation efforts require an understanding of the basic behavior and ecology of target species. However, limited information exists for a wide range of taxa, including declining species of rockfish (genus Sebastes). First, we observed captive juvenile China rockfish (S. nebulosus) to determine how they interact with their environment and conspecifics. Juveniles exhibited site fidelity and territoriality. These aggressive interactions occurred within the context of size-biased dominance, centered on competition for structurally complex habitat. Given the apparent importance of structure and the absence of structure in typical hatchery environments, we then asked how the absence of structure affects future behavior. When barren-reared and structure-reared juveniles were combined into a structurally complex aquarium, barren-reared fish displayed less structure use and less site fidelity than structure-reared fish. However, after 1 to 2 weeks, barren-reared fish began to use structure and showed site fidelity that eventually equaled that of structure-reared juveniles, showing that those behavioral effects of the rearing environment were not permanent. Though these short-term effects may still impact survival after hatchery release, we were unable to detect significant effects on vulnerability to a predator (lingcod, Ophiodon elongatus) in laboratory trials.

A record of Sebastes schlegelii Hilgendorf, 1880 from Dutch coastal waters

Abstract Sebastes schlegelii , a western Pacific rockfish species, is reported for the first time for The Netherlands. The presence of an established population is possible and warrants further investigation. Key words : Sebastes schlegelii , rockfish, Scorpaenidae, exotic species In Dutch marine waters, non-indigenous species from the western Pacific are relatively common. Most of these species were first observed after 1964, when Pacific oysters ( Crassostrea gigas (Thunberg, 1793)) were imported into Europe (Wolff 2005). Among these Pacific species no fish species have yet been reported. Sebastes schlegelii Hilgendorf, 1880, a western Pacific rockfish species, caught in 2008 in the south-western coastal waters of The Netherlands represents the first example. The genus Sebastes , containing the rockfishes, is the most species-rich genus in the family Scorpaenidae (Teleostei: Scorpaeniformes) with approximately 110 species worldwide. Their highest diversity is in the North Pacific (Kai et al. 2003; Hyde and Vetter 2007). The rockfishes exhibit a great diversity in their morphology and ecology, exploiting coastal habitats ranging from shallow rocky areas to depths of about 1000 meters (Love et al. 2002; Nakabo 2002). Only four species are found in the North Atlantic:

Demersal fish assemblages in the Southern California Bight based on visual surveys in deep water

Between 1995 and 2006, manned submers- ible fish surveys were conducted on the sea floor throughout the Southern California Bight. A total of 401 dives (comprising 1,015 transects and 14,373 habitat patches) were made in waters between 19 and 365 m deep. All natural habitat types were included, although both soft sea floors and rocky reefs were surveyed more than any other type. A total of 717,526 fishes, representing a minimum of 137 species and 47 families, were observed. Rockfishes (genus Sebastes), with a minimum of 50 species and 647,495 individ- uals (90.2% of all fishes observed), dominated most of the habitats. The most abundant species, squarespot (Sebastes hopkinsi), halfbanded (Sebastes semicinc- tus), shortbelly (Sebastes jordani), and pygmy rock- fishes (Sebastes wilsoni), are dwarf taxa that either school or aggregate. The most abundant non-rockfish species was the benthic and territorial blackeye goby (Rhinogobiops nicholsii). Both species richness and overall fish densities were highest in the shallowest sites. Most of the fishes in all habitats were small (≤20 cm TL long) and economically important species were generally uncommon. Forty-four species were found to be characteristic of the study area (occurring in at least 5% of the transects) and these species formed three faunal associations centered around depths of 62, 105, and 168 m. Based on size frequency distributions, at least 18 of the characteristic species exhibited ontogenetic movements, with young-of-the-year and older juveniles living in relatively shallow waters and larger individuals generally in deeper depths. In this study, the abundance of juvenile widow rockfish (Sebastes entomelas), and the virtual absence of adults, in southern California waters may demonstrate an ontogenetic northward movement of this species. This research implies that substantial harvesting of larger species by commercial and recreational fishers has helped alter some fish assemblages, allowing small and "weedy" species to thrive.

Trophic and fishery interactions between Pacific hake and rockfish: effect on rockfish population rebuilding times

Several species of overfished Pacific rockfish (genus Sebastes) are incidentally caught in the fishery targeting Pacific hake Merluccius productus. Juvenile rockfish also comprise a small amount of Pacific hake diets. We used 2-species, age-structured models to estimate how prey selectivity by Pacific hake, life history and population structure of rockfish, spatiotemporal overlap, and fishery closures might affect the time required to rebuild overfished rockfish populations to 40% of unfished spawning stock biomass. As prey selectivity increased, rebuilding time increased moderately for widow rockfish S. entomelas and darkblotched rockfish S. crameri, and more sharply for canary rockfish S. pinniger. Darkblotched rockfish were the least sensitive to Pacific hake predatory selectivity, which was likely related to their rarity in Pacific hake diets, not their stochastic reproductive success. Spatiotemporal overlap between rockfish and Pacific hake also increased rebuilding times, primarily because of higher rockfish bycatch, not predation. Early fishery closures and Pacific hake predation had an interactive effect that prolonged widow and canary rockfish rebuilding times, partly as a function of model assumptions and partly because fishery closures led to increased predation on juvenile rockfish. Because an ecosystem-based approach to fisheries management involves considering the influence of ecological factors on fish populations, models that examine interactions between depleted species and predatory species are essential. In this case, it appears that overfished rockfish rebuilding times can be significantly affected by the dynamics of a key predator, but also that the predatory effect can be mitigated by effective bycatch control.

An impediment to consumer choice: Overfished species are sold as Pacific red snapper

Concern over the collapse of many wild-caught fisheries has led to a recent focus on seafood-certification and consumer-driven support of sustainable seafood. However, such conservation strategies depend critically on the accurate labeling of seafood species in marketplaces. Pacific rockfish, a group of >60 species in the genus Sebastes, are often marketed as Pacific red snapper, but little is known about the number and identity of rockfish species sold under this name. We used a molecular approach to identify species sold as Pacific red snapper by grocery chains, local fish markets, and sushi restaurants in California and Washington. Using genetic data from two mitochondrial markers (cytochrome- b and control region), we identified seven species of rockfish ( Sebastes spp.), tilapia ( Oreochromis spp.), and one true red snapper ( Lutjanus campechanus) in our samples. Among samples identified as rockfish, 56% were identified as species listed as overfished by the National Marine Fisheries Service within the past three years. By effectively permitting all species of rockfish to be sold under a common vernacular name, state and federal agencies compromise the ability of consumers to make informed choices when buying seafood.

Maternal effects in rockfishes Sebastes spp.: a comparison among species

In temporally variable environments, longevity is generally considered to be a bet- hedging adaptation in which reproductive effort is spread across many years, increasing the proba- bility that favorable conditions for larvae will be encountered at least some time in a female's life span. A long reproductive life span provides the potential for individual females to exhibit inter- annual differences in energy allocation patterns that may be age- or size-dependent. We examine the effects of maternal age and size on larval quality, fecundity, and timing of parturition in 5 species of live-bearing rockfishes in the genus Sebastes (blue, yellowtail, olive, gopher, and kelp rockfish), and compare these maternal effects with previously documented patterns in black rockfish Sebastes melanops. Larval quality was indexed by size (notochord length) and condition (lipid storage in the oil globule). Maternal effects were found for oil globule size in blue, yellowtail and gopher rockfish, for weight-specific fecundity in blue and yellowtail rockfish, and for parturition date in blue, yellow- tail, and kelp rockfish. In all cases the maternal effects were similar to those reported for black rock- fish, with increasing lipid provisioning of larvae, greater weight-specific fecundity, and earlier timing of parturition in the spawning season with increasing maternal age or size. No effect of maternal age or size on larval size was observed. In general, maternal effects were more evident in winter spawn- ing species of the subgenus Sebastosomus (black, blue, olive, and yellowtail rockfish) than the spring spawning species of the subgenus Pteropodus (gopher and kelp rockfish). These results confirm that older and larger females in rockfish populations may contribute disproportionately to larval recruit- ment by producing higher quality larvae and more larvae per unit biomass, and releasing them at a different time than younger and smaller females. A shift in timing of parturition with female age may constitute a diversified bet-hedging strategy, providing a temporal spread of spawning effort within a maternal lineage, whereby successive female progeny release larvae at different times within the same year.

Multiple paternity and maintenance of genetic diversity in the live-bearing rockfishes Sebastes spp.

The understanding of mating systems is key to the proper management of exploited spe- cies, particularly highly fecund, r-selected fishes, which often show strong discrepancies between census and effective population sizes. The development of polymorphic genetic markers, such as codominant nuclear microsatellites, has made it possible to study the paternity of individuals within a brood, helping to elucidate the species' mating system. In the present study, paternity analysis was performed on 35 broods, representing 17 species of the live-bearing scorpaenid genus Sebastes. We report on the finding of multiple paternity from several species of Sebastes and show that at least 3 sires can contribute paternity to a single brood. A phylogenetically and ecologically diverse sample of Sebastes species was examined, with multiple paternity found in 14 of the 35 broods and 10 of the 17 examined species, we suggest that this behavior is not a rare event within a single species and is likely common throughout the genus. Despite high variance in reproductive success, Sebastes spp., in general, show moderate to high levels of genetic diversity. We suggest that multiple paternity may be a form of bet hedging that serves to maximize genetic diversity within broods and that, regardless of the selective value at the level of individual fitness, the net effect at the population level may be a genetic buffer to the consequences of severe overexploitation.

Incipient speciation within a subgenus of rockfish (Sebastosomus) provides evidence of recent radiations within an ancient species flock

The high frequency of speciation events associated with species flocks (i.e., radiations of closely related species) provides invaluable insight into the speciation process. Investigations of the speciation process in the marine environment are rare, and therefore, the genetic analysis of the rockfish genus Sebastes, considered an ancient marine species flock, provides an opportunity to investigate this process in the sea. Using both mitochondrial and nuclear markers, we analyzed five closely related species within the rockfish subgenus Sebastosomus. Our goal was to understand the evolutionary history and genetic relationships among species within this group and to provide evidence of recent speciation events within the subgenus. In the genetic analysis of the subgenus, we found different stages of the speciation process, with greater genetic divergences among three of the five species, evidence of recent divergence between two of the five species, Sebastes entomelas and S. mystinus, and significant genetic divergence between two lineages within S. mystinus revealing a signature of incipient speciation. We also found frequency differences of the two S. mystinus lineages among sample locations and found no evidence of introgression between the lineages at the location where both coexist. Although Sebastes is an example of an ancient species flock, this study provides evidence of ongoing speciation within the genus and reveals stages of this process from incipient to distinct species.

Resolving species identification problems in the genus Sebastes using nuclear genetic markers

The identification of North Atlantic redfish has been controversial and remains a difficult task due to overlapping of meristic and morphological characters. Here we used nine microsatellite loci to assess the level of genetic differentiation among these species and assess the resolution power of these microsatellite loci for individual assignment-based analyses. Conventional analyses as well as individual Bayesian assignment methods clearly separated the four species of North Atlantic redfish as well as the giant form of Sebastes marinus and the so-called “oceanic” and “deep-sea” types of Sebastes mentella. Locus-by-locus analyses revealed that only five microsatellite loci out of nine used could discriminate the concerned species. The advantage of the Bayesian methods relies in the individual information retrieved. It therefore gave additional information on the interrelationship among species. Indeed, we provide evidence of potential hybridization among species as well as individual misclassification based on morphological identification. We provide a powerful tool to discriminate North Atlantic redfish species, which might be useful for legal issues such as poaching, unintentional harvesting and control label.