Ocean Perch Research Articles

Ichthyophonus and Mycobacterium‐like bacterial infections in commercially‐important rockfish, Sebastes spp., in the eastern North Pacific Ocean

Recently there has been an increased concern about the status of demersal ®sh stocks, particularly rock®sh, Sebastes spp. (family Sebastidae), in the Paci®c Northwest (Musick, Harbin, Berkeley, Brugess, Eklund, Findley, Gilmore, Golden, Ha, Huntsman, McGovern, Parker, Poss, Sala, Schmidt, Sedberry, Weeks & Wright 2000). Offshore (slope and shelf) rock®sh ®sheries of particular concern (i.e. those that have declined signi®cantly in recent years) include canary rock®sh, Sebastes pinniger (Gill), widow rock®sh, S. entomelas (Jordan & Gilbert), Paci®c Ocean perch, S. alutus (Gilbert), yellowtail rock®sh, S. avidus (Ayres), and boccacio, S. paucispinus (Ayres) (Paci®c Fisheries Management Council 2000). Examples of rock®sh species that are considered at risk include S. pinniger and S. alutus, which are listed as `vulnerable' with a 77±93% and 81±91% decline, respectively. Sebastes avidus stocks are at 63% of pristine levels, but this stock is expected to decline because of poor recruitment (Paci®c Fisheries Management Council 2000). In a recent survey of marine ®sh for salmon pathogens conducted off the coast of British Columbia, we found that about 30% of the rock®sh examined were infected with the chlamydialike agent responsible for epitheliocystis, but most were light infections with insigni®cant associated pathological changes (Kent, Traxler, Kieser, Richard, Dawe, Shaw, Prosperi-Porta, Ketcheson & Evelyn 1998). In addition, Kent & Myers (2000) described severe liver lesions in redstripe rock®sh, S. proriger (Jordan & Gilbert), associated with a putative herpes virus. In 2000, Fisheries and Oceans Canada and Oregon Department of Fish and Wildlife research scientists conducted stock surveys of demersal ®sh, and we used this opportunity to conduct disease examinations of these ®sh to elucidate possible roles that diseases play in the demise of some of these stocks. Four species of rock®sh (S. alutus, S. avidus, S. reedi and S. pinniger) were examined from collections conducted off the coasts of Oregon on 5 May 2000 (latitude 44.35.00 N) and 20 September 2000 (latitude 44.40.00 N), and Washington (latitude 46.30.00 N) on 10 May 2000, except that S. reedi was not examined in the latter. An additional collection of S. alutus and S. avidus from Oregon was examined in September 2000. Also included here are data from 89 S. avidus, 56 S. alutus and 56 S. pinniger collected from three localities off British Columbia in the summer of 1999 (Table 1). The southernmost area in British Columbia was off the West coast of Vancouver Journal of Fish Diseases 2001, 24, 427±431

Co-existing populations of Pacific ocean perch, Sebastes alutus , in Queen Charlotte Sound, British Columbia

Variation at five microsatellite loci (Sal1, Sal2, Sal3, Sal4 and Sal5) was examined in approximately 1300 Pacific ocean perch (Sebastes alutus) sampled from 14 coastal sites in British Columbia, Canada. Mean observed heterozygosities by locus ranged from 71% to 88%, and by sample ranged from 75% to 84%. Theta values ranged from 0 to 0.04 over the five loci, and averaged 0.015. Among Pacific ocean perch samples, θ ranged from 0.001 to 0.056. Canonical discriminate analysis of multilocus genotypes and neighbour-joining analysis of pairwise genetic distances between samples both indicated the presence of three populations, one off the west coast of Vancouver Island (the Vancouver Island population) and two co-existing populations in Queen Charlotte Sound, Dixon Entrance and along the west coast of the Queen Charlotte Islands (the eastern and western QCI populations). Pacific ocean perch of the eastern and western QCI populations were caught in close proximity to each other, but individual samples showed little evidence of admixture. Fall and spring samples collected within geographic areas were genetically similar, indicating seasonally stable population structure. Restricted gene flow between the Vancouver Island and the two more northerly populations may result from limited adult dispersal and larval retention within the California Current and Alaska Gyre, respectively, but the presence of two populations within Queen Charlotte Sound cannot be explained entirely by larval retention hypotheses. The presence of two Pacific ocean perch populations in central British Columbia has implications for fisheries management.

The redfish species Sebastes viviparus, Sebastes marinus and Sebastes mentella have different composition of their tissue fatty acids

The fatty acid profile in the tissue of heart, gill, skull- and otolith-oil of the three redfish species, Sebastes viviparus, S. marinus and S. mentella was determined by a chemometric method, consisting of methanolysis of samples of the tissues and of the oils and gas chromatography of the resulting fatty acid methyl esters. The analytical data were treated by multivariate statistics comprising principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). Although the differences in fatty acid composition among the two tissues and two oils were the dominating features of the data, the three species had significantly different fatty acid profiles within each tissue. Variation among the individuals was considerable. The fatty acid profiles appeared to be species specific. The mutual relationship between S. marinus and S. mentella is closer than the relationship between either of them and S. viviparus. A comparison with a corresponding investigation on the same three species from another location indicates that the observed differences do not seem to be affected by biotic or abiotic factors.

Aluminium levels of fish fillets baked and grilled in aluminium foil

During storage and preparation of food, aluminium foil is often used for wrapping heat-sensitive raw food for protection against direct heat, e.g. grilled or baked fish fillets. In this investigation the aluminium contents of grilled and baked fish fillets with and without ingredients wrapped in aluminium foil were determined. The selected fish species were mackerel (Scomber scombrus L.), a fatty species, ocean perch (Sebastes spp.), a medium fatty species, and cod (Gadus morhua) and saithe (Pollachius virens), two lean fish species. The wrapped fillets were baked for approximately 20 min at 200°C in an oven, either without ingredients or, alternatively, with vinegar and sodium chloride added. In another experiment one part of a fillet was grilled over charcoal without ingredients and the other part was grilled with onion rings and mixed spices added. All aluminium concentrations of both baked and grilled fillets wrapped in aluminium foil increased during heating. The increase in aluminium concentration ranged from a factor of 2 (baked saithe fillets without ingredients from 0.10 up to 0.21 mg/kg) to a factor of 68 (grilled mackerel fillets with ingredients from 0.07 up to 5.04 mg/kg). The aluminium contents of grilled fillets were higher than those of baked fillets. Presumably two factors were responsible for the higher aluminium contents in grilled fillets: first the higher temperature of preparation when grilling fillets and second the high aluminium content of mixed spices (63.5 mg Al/kg), which may be taken up in part by the grilled fillets. All results clearly showed that some aluminium migrated from the aluminium foil into the food. The aluminium migration seems to depend on several factors, e.g. the duration and the temperature of heating, the composition and the pH-value of food, the presence of any other substances (such as organic acids and salt) and complexing reactions that result in dissolution of the complexed metal. Considering the present state of knowledge and the suggested provisional tolerable daily intake of 1 mg Al/kg bodyweight per day of the [World Health Organisation, 1989], no risk to health of the consumer would to be expected from eating meals prepared in aluminium foil.

Habitat-specific distribution of Pacific ocean perch ( Sebastes alutus) in Pribilof Canyon, Bering Sea

Shelf edge canyons are well-known sites of enhanced biomass due to on-shore transport and concentration of zooplankton along their axes, both of which contribute to the high densities of nekton frequently found in these canyons. Using a combination of acoustics, trawling, and in situ observations with a remotely operated vehicle (ROV), the distribution of pelagic and demersal biota within Pribilof Canyon in the Bering Sea was examined in September of 1995 and 1997. Near-bottom acoustic scattering patterns in the 38 kHz data showed high concentrations of biomass beginning around the 180 m bottom depth contour and continuing to about 220 m, which were presumed to be adult fish based on their target strength distributions. The 120 kHz data also showed very strong scattering in the water column between 150 and 175 m, which was absent from the 38 kHz data, and therefore attributed mainly to zooplankton. The dominant taxa collected in bottom trawls and mid-water plankton tows were adult rockfishes (Pacific ocean perch, Sebastes alutus) and euphausiids ( Thysanoessa spp.), respectively. In situ videos revealed dense aggregations of these rockfishes inhabiting a “forest” of attached sea whips, Halipteris willemoesi, during night deployments of the ROV, while areas with damaged sea whips had far fewer rockfish, and areas without this biotic habitat structure had no rockfish. During the day, the rockfishes were seen above the “forest”, where they were apparently feeding on dense swarms of euphausiids. It appears that these rockfish utilize this predictable and abundant food resource in the canyon during the day and are associated with the sea whip habitat at night during periods of inactivity. More research is needed on these slow-growing biotic habitats and how fishing activities in the Bering Sea and elsewhere may impact these habitats.

"Spring rise" of whaleworm (Anisakis simplex; Nematoda, Ascaridoidea) third-stage larvae in some fish species from Norwegian waters.

The seasonal variation in the infection of saithe (Pollachius virens), cod (Gadus morhua), and redfish (Sebastes marinus) from a coastal area of central Norway with Anisakis simplex third-stage larvae (L3) was studied over a period of 1 year. In all three host species there was an increase in the abundance of the parasite in spring, with a peak appearing in March and April. Cod displayed the most distinct seasonal variation, showing a clear abundance peak in April. The abundance peak in April for redfish was not as pronounced. In saithe the abundance over the seasons was less prominent, with a maximum appearing in March and another increase in abundance occurring during July. It is apparent that the causes behind the pattern of infection observed in this study are complex. However, possible explanatory mechanisms are discussed. Arguments are propounded to suggest that the increased supply of parasite eggs from northward-migrating whales in addition to the general spring bloom of plankton constitute the most important factors governing the phenomenon of "spring rise" in A. simplex L3 in the study area.

Discrimination of Sebastes viviparus, Sebastes marinus and Sebastes mentella from Faroe Islands by chemometry of the fatty acid profile in heart and gill tissues and in the skull oil

The composition of fatty acids in the tissue of heart, gill and skull oil of the three redfish species, Sebastes viviparus, Sebastes marinus and Sebastes mentella was determined by a chemometric method. The method consists of methanolysis of samples of the tissues and of the oils, gas chromatography of the resulting fatty acid methyl esters and multivariate statistical treatment, by principal component analysis, of the analytical data. Although the differences in fatty acid composition among the three tissues were the dominating features of the data, the three species had significantly different fatty acid profiles within each tissue, even though variation among the individuals was considerable. The fatty acid profiles appear to be species specific. The mutual relationship between S. marinus and S. mentella is closer than the relationship between either of them and S. viviparus.

Determination of aluminium in the edible part of fish by GFAAS after sample pretreatment with microwave activated oxygen plasma

An analytical method for the determination of aluminium in the edible part of fish was developed using a new pre-treatment method in a microwave activated oxygen plasma and graphite furnace atomic absorption spectrometry. The linearity of the calibration line as well as of different standard addition lines were very good within the measurement area of 0–60 μg Al/L. The recovery with spiked ocean perch fillet was good. The unsatisfactory recovery of aluminium with the reference-material (mussel tissue) may be due to high quantities of insoluble aluminium-silicates. An installed quality-control-card indicated that the method showed no significant fluctuation as well as contamination over the complete analysis time. The limit of detection calculated as 3 times the standard deviation of the blank absorbance divided by the slope of the calibration line was 1 μg Al/L.

Anisakidae larval infection in fish fillets sold in Belgium

Summary Fish fillets (n= 1760) sold on the Belgium market were examined for Anisakidae larval infection. Seven sea fish species were examined by means of the candling technique over a period of 4 months, from November 1996 to February 1997. Third‐stage larvae of Anisakis simplex and Pseudoterranova decipiens were identified. A. simplex was the most abundant species with a prevalence of 84.5%, and was found in 192 of the examined fillets (10.9%). Pollock (Pollachius pollachius) was the most heavily infected fish species (82.9%). The prevalence in cod (Gadus morhua), saithe (Pollachius virens), and whiting (Merlangius merlangus) was 34.7%, 26.7%, and 15.4% respectively. The prevalence in the three other fish species examined was low, namely 8.9%, 6.6%, and 3.8% for ling (Molva molva), catfish (Anarchias lupus), and Northeast red fish (Sebastes marinus), respectively. Pollock was the fish species with the largest number of Anisakis larvae (7.8 larvae/kg fish fillet).

Cod-end mesh size selection for rockfish and flatfish of the US West Coast

Size selection characteristics of five cod-ends (114-mm, 127-mm and 140-mm diamond, and 114-mm and 127-mm square meshes) were tested through alternate-haul experiments performed under commercial fishing conditions in 1988–1990, with a 76-mm diamond mesh cod-end as standard. Overall selectivity curves for five flatfish species (arrowtooth flounder, Atheresthes stomias, and Dover, Microstomus pacificus, english, Parophrys vetulus, rex, Glyptocephalus zachirus, and petrale sole, Eopsetta jordanii) and five rockfish species (shortspine thornyhead, Sebastolobus alascanus, Pacific Ocean perch, Sebastes alutus, and widow, S. entomelas, yellowtail, S. flavidus, and canary rockfish, S. pinniger) were estimated using the Share Each Length Catch Total (SELECT) method and four types of selection ogives (logistic, probit, negative extreme value and Gompertz) on weighted pooled length distributions. The negative extreme value curve provided the best fits to more than half of the data, implying asymmetry in the retention of small and very large fish. Lengths of 50% retention increased with increasing mesh sizes for both the diamond and square mesh cod-ends, with rockfish providing on average larger values than flatfish. In general, the 114-mm square mesh cod-end retained more small fish than the other cod-ends. Thus, compared to the currently used 114-mm diamond mesh, it is not a good alternative to reduce discard or retention of immature fish. On the other hand, the 127-mm square and diamond, and 140-mm diamond mesh cod-ends reduced the retention of immature fish for many of the species. Thus, these cod-ends seem acceptable for biologically conservative management regulations.

Visualizing catch–age analysis: a case study

Catch-age analysis has become a standard tool for modern stock assessment. Widely available graphical techniques can be customized to provide an intuitive framework for this complex procedure. We illustrate a graphical approach using data from a stock of Pacific ocean perch (Sebastes alutus). These data encompass typical problems in stock assessment, with missing data for some years and changes in age determination and survey methodologies midway through the time series. Preliminary visual inspection of the raw data reveals important features that must be accommodated in the model development. We tailor a state-space model to address these requirements and provide appendices that completely define the model and its statistical application. We suggest graphical methods for evaluating model output, including residuals and standard errors of population biomass. Such portrayals of uncertainty help define realistic limits to the information inherent in fishery data.

Development and ecology of ocean perch larvae, Helicolenus percoides (Richardson, 1842) (Pisces:Scorpaenidae), from southern Australian waters, with notes on the larvae of other sympatric scorpaenid genera

Helicolenus percoides development is described and illustrated from a series of larvae (n = 55; body length (BL), 1.9–12.3 mm) collected from waters around Tasmania, Australia. Broad-scale spawning occurred throughout the study area from late winter to late summer. Helicolenus larvae are characterized by a spongy tissue mass at the dorsal midline of the trunk. Larvae have 23–25 myomeres, a large finfold, three distinct areas of pigment (head, gut, and ventrally on the tail), a deep body, and a coiled, compact gut. Parietal, pterotic, preopercular, opercular, supraocular, post-temporal and supracleithral spines form by late notochord flexion. Fin development commences in the following sequence: pectoral, caudal, dorsal/anal simultaneously, and pelvic, with all fin elements present by 9.0 mm BL. H. percoides larvae are distinguished from the larvae of three other Tasmanian scorpaenid genera (Gymnapistes, Scorpaena and Neosebastes) by pigmentation, spination, morphometrics and meristics.This study addressed the question of variation within the larvae of H. percoides species. Except for variations in ventral body pigment, no differences were found to adequately support the separation of larvae examined into more than one species.

Factors affecting the annual abundance and regional distribution of English inshore demersal fish populations: 1973 to 1995

The 2 m beam trawl and 1.5 m push net were used to sample the small epibenthic fish assemblage during September on the east and south coasts of England. Fishing stations were distributed along the entire coast within four depth bands to 20 m. A total of 104 species were caught between 1973 and 1995, and these included infrequent Lusitanean species such as the big-scale sand-smelt (Atherina boyeri), and the undulate ray (Raja undulata), and infrequent boreal species such as the Norway haddock (Sebastes viviparus). Fifty-four taxa were selected as representative of the small, demersal inshore fish community that would be most vulnerable to capture by the two sampling gears, and were used in subsequent analyses of community structure. The north-east coast assemblage was the least diverse (H*=1.58) and least even (J*=0.47). It also supported the least number of species (55), and the variation in catch of the only dominant genus, Pomatoschistus spp., was partly responsible for large year-to-year variations in diversity and in the total population abundance of selected demersal species. On the east and south-east coasts, both diversity (H*=1.78 and 1.93) and evenness (J*=0.50 and 0.51) were greater than in the north, as a result of larger numbers of species available to the gears, and several species with relatively high catch density, such as Pomatoschistus spp., dab (Limanda limanda), solenette (Buglossidium luteum), and dragonet (Callionymidae). As a result, thefish assemblages of these coasts showed lower inter-annual variation in evenness and diversity. Trends in mean catch density of some species were correlated with the mean surface water temperature and salinity, especially for species which were near the edge of their normal geographic distribution in the southern North Sea. In addition, mean surface water temperatures were positively correlated with the total number of Lusitanean species on the south coast. These data provide evidence that during a period of more than 20 years, hydrographic factors have not only aVected species abundance, but, at low density, also their presence or absence in catches. ? 1996 International Council for the Exploration of the Sea

Impact of fish distribution and species composition on the relationship between acoustic and swept-area estimates of fish density

Bottom-trawl catches were compared with echo-integrator records obtained from a hull-mounted transducer on the towing vessel to examine how far from the bottom fish were available to the trawl. Swept-area density estimates obtained using a length-dependent effective fishing width were converted to equivalent echo-integrator values before being compared with the observed integrator values at different heights above the bottom. For large haddock (Melanogrammus aeglefinus (L.)), saithe (Pollachius virens (L.)), cod (Gadus morhua L.), redfish (Sebastes marinus (L.), and S. viviparus Krøyer) the best correlation between catch and acoustic data was obtained when applying the cumulative acoustic value (from the bottom upward) at 30 to 100 m above the seabed, while for Norway pout (Trisopterus esmarkii Nilsson) the best correlation was obtained at about the height of the headline of the trawl (4 m). Attempts to compensate the acoustic values for losses in the acoustic dead zone did not improve the correlations.

Monitoring Quality of Packaged Pacific Ocean Perch (Sebastes alutus) in Storage

Pacific ocean perch stored under vacuum, 100% CO2 or air at -3°C and 3°C was subjected to sensory, trimethylamine (TMA), color, microbial and volatile analyses. Unpleasant sensory attributes, TMA and microbial content were negatively correlated to overall quality, and Hunter 'L' value increased with storage time. Principal factor analysis of sensory data resulted in three factors that accounted for 71% of the variance, with factor 1 (53%) mainly related to poor quality attributes. Volatiles analyzed by the dynamic headspace technique included alkanes, alkenes, aldehydes, aromatics and alcohols. Canonical variate analysis on volatile compounds separated excellent and poor quality fish samples, while good and medium samples were grouped together.

Influence of spoilage and processing temperature on the quality of marine fish protein sources for salmonids

Press cake meals were prepared from previously frozen herring immediately following thawing and after storage for 8 or 12 days at 2-5°C. Each of the raw sources of herring was subjected to two processing temperatures, 75°C and 100°C, during meal preparation. Also, protein hydrolysates were prepared using ocean perch when fresh or after storage at 2-5°C for 4 or 8 days. Subsequently, each of the three hydrolysates was dried at 85°C or 93°C. In two separate experiments, each of the herring press cake meals and dried perch protein hydrolysates was blended with a reference diet in a 30:70 ratio (test protein source: reference diet). All diets contained 5 g kg−1 chromic oxide as an indigestible marker. The reference diet and all test diets were provided to satiation to chinook salmon in salt water and rainbow trout in fresh water, with digestibility of organic matter, protein and energy measured by difference. Digestibility of protein was also measured by the pH-stat and dilute pepsin solubility in vitro techniques. The results indicated that variation in processing temperature to a maximum of 100°C had little effect on digestibility of marine fish protein sources. By contrast, raw material storage for 8 days or more at 2-5°C prior to processing was found to reduce organic matter digestibility and sometimes nitrogen digestibility in salmonids. In vitro measures of digestibility were of little help in predicting the nutritive value of the test protein sources. Cadaverine level in herring press cake meal was shown to be a good indicator of spoilage in the raw material.

Decision analysis of alternative harvest policies for the Gulf of Alaska Pacific ocean perch fishery

By the mid-1970s the estimated biomass of Pacific ocean perch (POP), Sebastes alutus, in the Gulf of Alaska (GOA) had been reduced to about 10% of the estimated level present during the early 1960s. Although fishing mortality was greatly reduced, the stock has shown only modest increases in biomass; the current estimate of spawner biomass is between 15% and 20% of the estimated peak levels. This decline has raised concern that past management measures may have been inadequate to allow growth of the POP stock in the GOA. Consequently, we performed an analysis to: (a) identify optimal fishing rates for rockfish species such as Pacific ocean perch, (b) identify the biomass level that would produce an optimum yield, and (c) evaluate alternative fishing policies designed to improve the condition of the POP resource. The selection of an optimal fishing rate for POP in the GOA was based on a maximin criterion. Recruitment variability was shown to play an important role in determining the effects of different harvest policies. Based on estimates of optimal biomass and fishing mortality rates, four alternative harvest policies were developed and evaluated using a stochastic simulation model. These policies ranged from harvests based on rates under the status quo policy to increasingly restrictive measures. Policy outcomes were measured in terms of yield in weight and dollar-value, female spawner biomass, and risks. We presented the results in the form of Bayesian decision tables. The ability to predict future stock levels with a high degree of certainty is poor. In no case is there a guarantee that rebuilding will occur.

Oceanographic features that define the habitat of Pacific ocean perch, Sebastes alutus

This study investigates the possibility that oceanographic features could have effects on the variations observed in the apparent abundance of a demersal rockfish, Pacific ocean perch, Sebastes alutus. Simultaneous monitoring of physical variables and indices of fish abundance was achieved by attaching oceanographic equipment to the fishing gear of commercial vessels and sampling the fish catch. It was found that perch prefer a temperature range from at least 4.8d̀C to 6.7d̀C and that their movement patterns are linked to the movement of these temperatures by coastal wind patterns. Perch prefer areas with steep bathymetry, characterized by turbulent activity due to interactions between the local bathymetry and tidal currents.

Storage Quality of Fresh and Frozen‐thawed Fish in Ice

ABSTRACTThe objective was to determine whether traditional quality indexes of fresh (unfrozen) fish like sensory analysis, bacterial counts and trimethylamine content could be applied to thawed whole cod, cod fillets and ocean perch fillets kept in ice. Freezing and short‐term freezer storage (≤5 wk at −25°C) had very little effect on bacterial counts. During long‐term freezer storage (≥14 wk at −25°C) total counts were reduced as well as counts of trimethylamine oxide‐reducing bacteria in cod fillets but not in ocean perch fillets. When the thawed fish was unacceptable the trimethylamine was <1 mgN/100g. Trimethylamine as a spoilage indicator was of no value when evaluating spoilage of thawed whole cod, cod fillets and ocean perch fillets kept in ice.

Trip Limits, Catch, and Effort in the British Columbia Rockfish Trawl Fishery

Trip limits (catch ceilings on individual fishing trips) have been used extensively in the management of groundfish trawl fisheries on the west coast of North America. Here, I describe some consequences of this management approach on the fishery for Pacific ocean perch Sebastes alutus off British Columbia. Before the implementation of trip limits, vessels regularly landed catches of over 50 metric tons (tonnes). In 1992, vessels on one fishing ground were restricted to Pacific ocean perch landings of less than 4.5 tonnes. Thus, trip limits have redistributed effort in the fishery, and a relatively constant annual catch is now attained through an increasing number of smaller trips. However, some catch in excess of the trip limit is known to be misreported as catch of other species; the discarding of excess catch at sea also occurs. Consequently, the catch and catch-per-unit-effort (CPUE) data required for stock assessment are underestimated. In particular, CPUE is positively correlated with the trip limit. Managers should consider the detrimental impact of trip limits on fishery-dependent abundance indices when new trip limits are implemented. Improved catch reporting and fishery-independent abundance indices could provide more accurate assessments.