Sebastes Mentella Research Articles

Genetic structure of deep-water redfish, Sebastes mentella , populations across the North Atlantic

Patterns of genetic diversity of the marine deep-water redfish, Sebastes mentella Travin, from 21 sampling locations (n=46 per sample, from 1995 to 1998) were examined throughout its range in the North Atlantic. Eight microsatellite loci were used in order to: (1) define the genetic structure and consider the possible influence of dispersal, geographic distance, oceanic currents and historical factors; and (2) relate the structure to present management units and practices. Three divergent population units (mean θ=0.012) associated with distinct geographic areas were defined: Eastern (Norway and Barents Sea), Panoceanic and Western (Gulf of St. Lawrence and offshore Newfoundland). The most important observation was the lack of genetic differences (mean θ=–0.0004) and lack of genetic isolation by geographic distance (r=0.318, P=0.112) among samples within the Panoceanic zone, from the Faroe Islands to the Grand Banks (6,000 km). A combination of vicariance, historical introgression with a closely related species, S. fasciatus, and contemporary patterns of oceanic circulation are likely to have shaped the observed population structure. These results only partially support current management units, and call for more integrated practices for regulating the exploitation of S. mentella throughout its extensive range.

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.

Studies of the genetic relationship between deep-sea and oceanic Sebastes mentella in the Irminger Sea

A joint venture between Iceland and Norway to study the beaked redfish, Sebastes mentella, in the Irminger Sea was undertaken in 1995. The genetic relationship of deep-sea and oceanic S. mentella in the Irminger Sea and their relationship to redfish groups in adjacent waters were studied by gel electrophoresis and isoelectric focusing of haemoglobin and allozymes. The oceanic type of redfish in the Irminger Sea occurred as a homogenous group, but differed from the deep-sea type. This result was mainly based on frequency distributions of the enzyme loci MEP-1* and IDHP-2* and minor haemoglobin components. Heterogeneity was found within the deep-sea type, which also showed similarities with beaked redfish from the Icelandic shelf area. One sample of “untyped” S. mentella found below 600 m resembled the oceanic type in morphology and gene frequencies. Both types of S. mentella differed from S. mentella from Canada and Norway, but they could not be distinguished from immature S. mentella from Greenland as far as could be judged from previous studies.

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.

Metazoan parasites of teleost fishes from atlantic waters off the Faroe Islands

Abstract 532 specimens belonging to 50 species of teleost fishes collected from shallow waters down to a depth of 1,540 m off the Faroes were examined for metazoan parasites. Ten or more specimens of the following fish species were examined: Argentina silus, Gasterosteus aculeatus, Ga-dus morhua, Melanogrammus aeglefinus, Merlangius merlan-gus, Micromesistius poutassou, Pollachius virens, Trisopterus esmarki, Molva dipterygia, Onogadus argentatus, Lycodes es-marki, L. pallidus, Sebastes mentella, S. viviparus, Myoxoceph-alus scorpius, Artediellus atlanticus, Cottunculus sadko, Para-liparis bathybius, Rhodichthys regina, Hippoglossoides plales-soides, Limando limando,, Microstomus kitt and Reinhardtius hippoglossoides. The nematodes were dealt with in a previous paper. In the present study 38 species of digeneans, with review of their life-cycles, are recorded. In addition, 8 species of monogeneans, 11 species of copepods, and 2 species of leeches, among other a 19 cm long specimen of Notostomum laeve, are recorded. Most acantho-cephalans are identified to genera and most cestodes are identified to order only. Most species are new to the Faroes.

A multivariate analysis of food and feeding trends among Greenland halibut (Reinhardtius hippoglossoides) sampled in Davis Strait, during 1986

Pelagic invertebrates [northern shrimp (Pandalus borealis), Cephalopoda, Mysidacea, Amphipoda and Euphausiacea] and fish [redfish (Sebastes mentella), R. hippoglossoides and Arctic cod (Boreogadus saida)] were the most important food items found in 4295 Greenland halibut (R. hippoglossoides) stomachs collected from Davis Strait [Northwest Atlantic Fisheries Organization (NAFO) Subareas 0 and 1], during 1986. Ordination methods indicated that predator size and capture depth accounted for 85.2% of the variation in diet, while classification methods were used to illustrate these relationships. Additionally, the study extended into locations not previously sampled, therefore, knowledge was expanded upon pertaining to the distribution ranges of important prey.

Digestive enzymes in marine species. II. Amylase activities in gut from seabream (Sparus aurata), turbot (Scophthalmus maximus) and redfish (Sebastes mentella)

The amylase activity of the digestive tract of three carnivorous fish species (Sparus aurata, Scophthalmus maximus and Sebastes mentella) has been studied. The activity of seabream and turbot showed its maximum at neutral pH (7.0–7.5); meanwhile, the activity of redfish had an optimum pH at 4.5-5.0. The t° function ranged between 35 and 45°C for the three species. The Arrhenius plots of the intestinal activities of seabream and turbot showed breakpoints at temperatures close to those of their physiological activities. High saline concentrations inhibited the activity of seabream and turbot and activated the activity of redfish. Seabream activity was absolutely dependent on calcium ions. On the contrary, redfish activity was only detected in the absence of this metal. Studies carried out by using several effectors suggested that the activities found in these three species are different. Considering our results from a point of view of the environmental conditions of these species, it might be concluded that enzymatic digestion of dietary carbohydrates proceeds at very low rate. Physiological implications are discussed.

Evaluation of threshold-induced bias in the integration of single-fish echoes

In fisheries acoustics the bias introduced by a threshold in the integration of echoes from fish and other marine organisms has long been recognized. This bias is especially evident when the fish are observed in scattered concentrations. The method proposed here for evaluating the threshold-induced bias in the integration of single-fish echoes requires that the target strength distribution of the fish and the directivity pattern of the transducer be known, as well as the integration threshold in terms of the scattering cross-section of the fish. It is shown that for transducers usually employed in fisheries acoustics, the threshold effect is for all practical purposes independent of the transducer in question, thus generalizing the effect for a specific distribution. Results from direct measurements of the threshold-induced bias in the echo integration of oceanic redfish (Sebastes mentella) at 38 kHz are presented and compared with results obtained by the method proposed. The validity of the assumptions made in the numerical calculations and the effect of possible deviations from the true situation are discussed.

Digestive enzymes in marine species. I. Proteinase activities in gut from redfish ( Sebastes mentella), seabream ( Sparus aurata) and turbot ( Scophthalmus maximus)

The proteolytic activities of the digestivetract of three carnivorous fish species ( Sebastes mentella, Scophthalmus maximus, Sparus aurata) have been studied. The activity found in the stomach showed a pH optimum of 2.0 for all species, whereas this was in the alkaline range (9.5–10.0) in the intestinal extracts. Similar optimal temperature was measured for all species, although higher residual activities were detected at low temperatures in redfish and turbot. Lower E a values were detected in stomach than in intestine. The effect of NaCl concentration on protein digestion differed between stomach and intestine being inhibitory in the former. The main proteolytic enzyme for the acid activity of the stomach of the three species seemed to be a pepsin. However, the enzymatic composition of the intestine was more species specific.

Determination of Fish Age Using 210Pb: 226Ra Disequilibrium Methods

Previous workers have used disequilibrium in the 210Pb: 226Ra ratio in fish otoliths to estimate the age of four teleost species: Hoplostethus atlanticus, Macruronus novaezelandiae, Sebastes diploproa, and Sebastes mentella. We argue that uncontrollable errors due to degassing of intermediate 222Rn from otoliths, unknown sources and sinks of 210Pb and 226Ra, possible changes in the ratio with which these isotopes are accreted to the otolith over the life of the fish, contamination by 210Po, difficulties in obtaining otolith cores, and the dependence of the estimated radiometric ages on the mass growth-in-time model usually adopted for otoliths can invalidate the application of disequilibrium techniques to fish age estimation.

Observations on Non-Maturing Redfish (Sebastes mentellaTravin)in the Northwest Atlantic

In the early-1960s a deepwater form of redfish (Sebastes mentella Travin) was found at depths more than 500 m on the continental slopes of Labrador and North Newfoundland. This group differed from the beaked redfish commonly distributed in these areas by the biological peculiarities of non-developed reproductive organs and lack of sexual dimorphism. The results of nearly 30-year observations showed that the form of non-maturing redfish had not changed. They were distributed along the continental slope northward of Div. 3K and the fish size increased from north to south. The distribution of this form of redfish was similar to that of non-maturing roundnose grenadier (Coryphaenoides rupestris). The origin and causes which led to inhibition of gonadal development of both groups were considered to be analogous. The non-maturing group of redfish was thought to originate from partial eggs and larval drifts from the Irminger Sea to form a pseudo-population in the area studied. The need for studies of the population and its exploitation of this potentially commercially valuable group is emphasized.

210Pb/226Ra Determination of Longevity in Redfish

Examination of annular growth rings apparent in charred otolith cross sections is the basis for reports of extreme longevity in the rockfish genus Sebastes, but the interpretation of the annuli has long been disputed. We used a radiochemical assay of the otolith core to confirm our interpretation of annuli in Atlantic redfish, Sebastes mentella, to at least an age of 65 yr. Through measurement of the radioactive disequilibrium between 226Ra and 210Pb, it appears that redfish live to an age of at least 75 yr in the waters off of Nova Scotia.

Biochemical separation of Atlantic Canadian redfish: Sebastes mentella and Sebastes norvegicus

One of the problems for management of the redfish fishery in the Gulf of St. Lawrence is the difficulty in distinguishing between the different species: deepwater redfish (Sebastes mentella), golden redfish (Sebastes norvegicus), and Acadian redfish (Sebastes fasciatus). Controversy exists concerning whether S. mentella and S. norvegicus are separate species because of similarity of meristic characters and other attributes. We describe a procedure that distinguishes these two forms by isoelectric focusing using polyacrylamide gels of water-soluble muscle proteins. In our samples, the lower part of the gel of S. mentella consistently shows three major protein bands, while that of S. norvegicus shows only one major band. The isoelectric focusing banding patterns from our study agree with those found by other workers for redfish from Greenland and Norway. The unequivocal isoelectric focusing separation and its concordance with morphometric characters indicate that S. mentella and S. norvegicus are genetically distinct, reproductively isolated species.

Chromatoblastomas and related pigmented lesions in deepwater redfish, Sebastes mentella (Travin), from North Atlantic areas, especially the Irminger Sea

Abstract This study involved 34 960 specimens of deepwater redfish, Sebastes mentella (Travin), from the North Atlantic, 21 460 of them from the Irminger Sea. One hundred and three specimens of this species, 96 with pigmented lesions, were examined histologically. The black patches on the redfish skin proved to be superficial melanosis (48 cases) and deep melanosis (24 cases). Skin pterinophorosis was noted in 20 cases. Pigment tissue neoplasms were observed in 26 fish; all were benign chromatoblastomas. Fourteen tumours were diagnosed as melanomas originating from melanophores, seven as pterinophoromas originating from pterinophores, and five as pterino‐melanophoromas or melano‐pterinophoromas of mixed origin of both chromatophore types. The tumours on the trunk of redfish occurred only in pigmented areas larger than 20 cm2. Fish with such areas constitute no more than 2.4% of the total Irminger Sea redfish population. Most (76.2%) of pigmented lesions in this redfish population did not exceed 5 cm2 in area. The arrangement of pigmented areas differed in males and females. In females, 97% of patches were found between the pectoral and the first dorsal fins, whilst in males, 84% of patches were situated on the head and caudal fin. Pigmented lesions occurred 2–5 times more often in females than males. The causes of pigment tissue neoplasms and pigmented lesions in deepwater redfish are unknown.

Development of deep-water redfish (Sebastes mentella) larvae, with comparative notes on newly extruded Acadian redfish (Sebastes fasciatus) from the Flemish Cap

Planktonic redfish larvae of the genus Sebastes were collected from Flemish Cap, an offshore Northwest Atlantic fishing bank east of the island of Newfoundland, Canada. A protocol based on discriminant function analysis and previously published age–length relationships was used to identify specimens of S. mentella and newly extruded (< 9 mm) S. fasciatus. On Flemish Cap, newly extruded larvae of S. mentella and S. fasciatus do not differ significantly in body proportions, fin morphology, or numbers of body myomeres but do differ significantly in pigmentation patterns on the head, nape, dorsal body midline, and numbers of subcaudal melanophores. A developmental series of S. mentella is described in terms of morphometry, meristics, occurrence of head spines, and pigmentation patterns and compared to previously published data on Sebastes spp. from other areas. The utility of various characters in relation to their use as identification criteria is discussed. The results of this morphological analysis support the contention that S. mentella and S. marinus larvae are more similar to each other than either of them is to S. fasciatus.

Quadratic Discriminant Analysis with Covariance for Stock Delineation and Population Differentiation: A Study of Beaked Redfishes (Sebastes mentella and S. fasciatus)

Stock delineation is of vital importance in fisheries management programs. Linear discriminant function (LDF) has been employed extensively in population differentiation studies but is of severely restricted usefulness when populations differ in their dispersion matrices. Quadratic discriminant function (QDF) is the appropriate analysis to employ in these situations. Here, I analyzed morphometric data of beaked redfishes (Sebastes mentella and S. fasciatus) by a recently developed conditional QDF.

Comparative morphology of preextrusion larvae of the North Atlantic sharp-beaked red fishes, Sebastes mentella and Sebastes fasciatus (Pisces: Scorpaenidae)

Preextrusion larvae of the ovoviviparous scorpaenid fishes, Sebastes mentella and Sebastes fasciatus, identified by the gas-bladder musculature characteristics of the parent, are described. Morphometrics, meristics, and pigmentation characteristics were recorded for late-stage preextrusion larvae taken from adult females on St. Pierre Bank, an area immediately south of and adjacent to the island of Newfoundland, Canada. The morphology of preextrusion larvae of S. mentella, in comparison with S. fasciatus, is described in detail for the first time. Univariate statistics were calculated and the utility of each of several morphometric, meristic, and pigmentation variables as a potential species identification criterion was evaluated. Discriminant analysis correctly classified up to 95% of larvae examined. The potential of the discriminant function in species identification for planktonic larvae is discussed.

Estimation of Partial Recruitment and Yield per Recruit for an Otter Trawl Fishery for Deepwater Redfish

Abstract The Canadian deepwater redfish (Sebastes mentella) fishery in the Atlantic ocean tends to be concentrated in a limited depth range to maximize catch rates and optimize size composition of the catches that vary with depth. Thus, the assumption of Beverton and Holt's yield-per-recruit analysis that all fish are equally subject to fishing mortality beyond a certain size seems inappropriate for this fishery. The alternative method of Thompson and Bell is more flexible but requires estimated age-specific, partial recruitment factors as an input. In this study, selectivity factors empirically determined for various bottom trawl mesh sizes and information from research vessel surveys on the composition of deepwater redfish catches in different depth zones were analysed to estimate partial recruitment factors for subsequent yield calculations. Partial recruitment factors were estimated for the commercial otter trawl fishery on deepwater redfish in Divisions 2J and 3K of the Northwest Atlantic Fisheries O...

Distinguishing Beaked Redfishes (Deepwater Redfish, Sebastes mentella and Labrador Redfish, S. fasciatus) by Discriminant Analysis (with Covariance) and Multivariate Analysis of Covariance

Analysis of morphometric data for differentiating fish species and stocks has frequently been unsatisfactory as a result of sampling bias associated with the varying size of specimens and the large overlapping of characters. These difficulties may be overcome by using a discriminant function with covariance and multivariate analysis of covariance. In a classification study of beaked redfishes, in which the specimens of Labrador redfish (Sebastes fasciatus) are relatively smaller than those of deepwater redfish (S. mentella), a single character would not separate species, but a compound criterion (discriminant function) of several characters separated the species effectively. A discriminant function with covariance separated species/populations remarkably well and better than one without covariance. Seven morphometric characters were identified as pertinent discriminators between S. fasciatus and S. mentella. As much as 89% of the total variation in the sample was accounted for by the discriminant function and only 8 out of 198 individuals (4%) were in the zone of uncertainty. It is explained why using a large number of characters in discriminant analysis may not be appropriate for samples of limited sizes. Also, expressing morphometric measurements as ratios, proportions, or percentages of body length may not be an appropriate way of reducing variation owing to size differences.

Meristic variation in beaked redfishes, Sebastes mentella and S. fasciatus, in the Northwest Atlantic

The distribution of Northwest Atlantic beaked redfishes, Sebastes mentella and S. fasciatus, has been confused for the past several decades. Sebastes fasciatus has been reported as having lower meristic counts than S. mentella. Meristic elements of 33 301 vertebrae, 22 622 anal fin ray, and 16 290 dorsal fin ray counts were utilized to examine the yearly, depth, and geographic variation of meristics in beaked redfishes. Data collected from specimens caught off West Greenland, Baffin Island, Labrador, Newfoundland, Quebec, and Nova Scotia were analyzed by 100-m-depth intervals. Temporal and depth variation were examined by the χ2-test of independence on meristic frequencies. Geographic variation was evaluated using the modes and mean values in the meristic frequency histograms. Cluster analysis of meristic frequencies displayed the dendrographic affinities and the distance matrix among division–depth blocks.Temporal variation indicated a mixture of vertebral frequency patterns which varied with depth and area. Depth variation and geographic clines were found for each of these meristic characters; the shallow and southern waters were dominated by counts of 29, 14–13, and 7 for vertebrae, dorsal fin rays, and anal fin rays, respectively, whereas deep and northern waters were dominated by 30, 15–14, and 8–9. These results suggested that S. fasciatus occurs on the Nova Scotian Shelf and Grand Bank whereas S. mentella is largely found in Baffin Bay, Labrador waters, and the Gulf of St. Lawrence. The common names of S. mentella and S. fasciatus are discussed. Additionally, five hypothetical stocks of beaked redfishes based on meristic patterns are proposed for management purposes.Key words: Sebastes mentela, S. fasciatus, redfish, meristic variation, distribution, cluster analysis