Population structure of beaked redfish (Sebastes mentella Travin, 1951) in the Irminger Sea and adjacent waters inferred from microsatellite data

Samples of beaked redfish from the Irminger Sea and adjacent waters were examined for polymorphism at ten microsatellite loci. The strategy of the material collection enabled investigation of geographic, bathymetric, and temporal variation of this species. The results did not support the evidence on spatial differentiation and temporal stability of the species distribution, favoring the idea that the water area examined was inhabited by a single pelagic population of beaked redfish.     

Growth Properties in Redfishes of the Genus Sebastes on the Flemish Cap Bank

Journal of Ichthyology - This article analyzes the dynamics of the linear growth rate for three redfish species of the genus Sebastes on the Flemish Cap bank: beaked redfish S. mentella, golden...     

Three‐dimensional post‐glacial expansion and diversification of an exploited oceanic fish

Vertical divergence in marine organisms is being increasingly documented, yet much remains to be carried out to understand the role of depth in the context of phylogeographic reconstruction and the identification of management units. An ideal study system to address this issue is the beaked redfish, Sebastes mentella – one of four species of ‘redfish’ occurring in the North Atlantic – which is known for a widely distributed ‘shallow‐pelagic’ oceanic type inhabiting waters between 250 and 550 m, and a more localized ‘deep‐pelagic’ population dwelling between 550 and 800 m, in the oceanic habitat of the Irminger Sea. Here, we investigate the extent of population structure in relation to both depth and geographic spread of oceanic beaked redfish throughout most of its distribution range. By sequencing the mitochondrial control region of 261 redfish collected over a decadal interval, and combining 160 rhodopsin coding nuclear sequences and previously genotyped microsatellite data, we map the existence of two strongly divergent evolutionary lineages with significantly different distribution patterns and historical demography, and whose genetic variance is mostly explained by depth. Combined genetic data, analysed via independent approaches, are consistent with a Late Pleistocene lineage split, where segregation by depth probably resulted from the interplay of climatic and oceanographic processes with life history and behavioural traits. The ongoing process of diversification in North Atlantic S. mentella may serve as an ‘hourglass’ to understand speciation and adaptive radiation in Sebastes and in other marine taxa distributed across a depth gradient.     

Features of the reproductive cycle in females of the beaked redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Sebastidae)

The reproductive status of some categories of females of the beaked redfish Sebastes mentella has been determined as a result of the histological analysis. The histological characteristic of gonads of large nonreproductive females of redfish is presented for the first time. Gonads of mature females that skip spawning are studied. The cytomorphological characteristic of ovaries after larvae extrusion is specified. A broadened maturity scale for gonads of females of S. mentella supplemented with stages that characterize fish that skip spawning and large nonreproductive females is proposed.     

Intraspecies structure of beaked redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> of the Atlantic and Arctic oceans

On the basis of the results of complex interdisciplinary investigations of the population composition and structure of the beaked redfish Sebastes mentella of the Atlantic and Arctic oceans, its three populations are discerned relatively isolated from each other by the system of permanent marine currents—North Atlantic, Flemish-Cape, and Norway-Barents Sea. The population structure of the species in the southern part of its area corresponds to the model of a local stock. Interaction of the North Atlantic and the Norway-Barents Sea populations well correspond to the model of fluctuating stocks. Redfish aggregations in different biotopes (mesobenthal and mesopelagial) are intrapopulational epigenetic groups. In the period of warm and anomalously warm years, a part of mature specimens from the pelagial of the North Irminger Sea make an irreversible migration to the southern part of the Norwegian Sea and form there mixed aggregations of fish from the North Atlantic and Norway-Barents Sea populations. With consideration of the effect of climatic–oceanological processes, a principally new scheme is elaborated describing the process of seasonal migrations of redfish in the mesobenthal and mesopelagial. The previous views on direction of return migrations of redfish of the Norway-Barents Sea population are reconsidered. Juveniles from the western part of the Barents Sea and Spitsbergen not only supplement the demersal aggregations but also migrate to the pelagial of the Norwegian Sea.     

New Data on the Distribution of Beaked Redfish Sebastes mentella (Sebastidae) in the Greenland Sea

Journal of Ichthyology - The ichthyological studies carried out at the shelf of North-Eastern Greenland in 2002–2017 new regions of dwelling of beaked redfish Sebastes mentella were...     

Ecological and Population Features of Beaked Redfish Sebastes mentella (Sebastidae) in the Northwest Atlantic Based on the Analysis of Its Parasite Fauna

Journal of Ichthyology - The results of studying the composition and features of the ecology, zoogeography, and formation of the parasite fauna of beaked redfish Sebastes mentella in the waters of...     

Parasites and Maturation Rate as Indicators of Population Structure in the Beaked Redfish Sebastes mentella (Sebastidae)

Journal of Ichthyology - The direction of phylogenesis of beaked redfish Sebastes mentella is considered based on a comparative analysis of the parasite fauna and maturation rate of individuals in...     

Parasites as Biological Tags for Stock Discrimination of Beaked Redfish (Sebastes mentella): Parasite Infra-Communities vs. Limited Resolution of Cytochrome Markers

The use of parasites as biological tags for discrimination of fish stocks has become a commonly used approach in fisheries management. Metazoan parasite community analysis and anisakid nematode population genetics based on a mitochondrial cytochrome marker were applied in order to assess the usefulness of the two parasitological methods for stock discrimination of beaked redfish Sebastes mentella of three fishing grounds in the North East Atlantic. Multivariate, model-based approaches demonstrated that the metazoan parasite fauna of beaked redfish from East Greenland differed from Tampen, northern North Sea, and Bear Island, Barents Sea. A joint model (latent variable model) was used to estimate the effects of covariates on parasite species and identified four parasite species as main source of differences among fishing grounds; namely Chondracanthus nodosus, Anisakis simplex s.s., Hysterothylacium aduncum, and Bothriocephalus scorpii. Due to its high abundance and differences between fishing grounds, Anisakis simplex s.s. was considered as a major biological tag for host stock differentiation. Whilst the sole examination of Anisakis simplex s.s. on a population genetic level is only of limited use, anisakid nematodes (in particular, A. simplex s.s.) can serve as biological tags on a parasite community level. This study confirmed the use of multivariate analyses as a tool to evaluate parasite infra-communities and to identify parasite species that might serve as biological tags. The present study suggests that S. mentella in the northern North Sea and Barents Sea is not sub-structured.     

Structure of aggregations and principal populational characteristics of redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Scorpaeniformes: Scorpaenidae) in the pelagic zone of the Irminger Sea and adjacent waters

The spatial distribution of redfish Sebastes mentella in the pelagic zone of the northern part of the Atlantic Ocean (the Irminger Sea and the Labrador Sea) is investigated. Analysis of the data on size-age composition, sex ratio, ratio of mature and immature specimens, rate of maturation, composition of the parasite fauna, infestation level, infestation with the copepod Sphyrion lumpi, and occurrence of pigment formations on the body of redfish from the investigated areas indicate the absence of stable isolated aggregations of this species in the oceanic pelagial of the North Atlantic. Pelagic aggregations are formed of rapidly maturating specimens migrated from the slopes of Greenland. The spatial variation of the size-age composition of redfish depends on the life cycle and regional hydrological conditions.     

Stejneger's beaked whale strandings in Alaska, 1995–2020

Presented here is the first comprehensive and updated compilation of history, distribution, and findings of Stejneger's beaked whales (Mesoplodon stejnegeri) in Alaska. Stejneger's beaked whales are a poorly understood, elusive, deep-diving cetacean species found in the North Pacific Ocean. Since Stejneger's beaked whale strandings data in Alaska through 1994 were last published, 35 additional strandings have been documented. Twenty-seven animals stranded in the Aleutian Islands, seven stranded in Southcentral Alaska, and one animal stranded on St. Lawrence Island. Twenty-two carcasses were necropsied, but only four were fresh. Seventeen of the 22 died during mass stranding events and cause of death could not be definitively determined. Barotrauma was suspected in three cases and infectious disease possibly complicated by barotrauma occurred in two cases. We documented an expansion of strandings into the northern Bering Sea, characterized a sex bias, examined stomach contents that included macroplastic, and identified parasites not previously associated with Stejneger's beaked whales. Also included are data on the largest known mass stranding of Stejneger's beaked whales, which occurred on Adak Island in 2018. The history, distribution, and findings presented here are central to further our understanding of this species.     

中国大陆海域沿岸搁浅和误捕的喙鲸类调查

从2009 年1 月至2010 年2 月,我们对中国大陆海域沿岸搁浅和误捕的喙鲸类头骨标本进行了测量和鉴
定。目前中国大陆海域搁浅和误捕的喙鲸类有5 种,分别为柯氏喙鲸、贝氏喙鲸、朗氏喙鲸、柏氏中喙鲸和小
中喙鲸,其中小中喙鲸为中国海域(包括台湾)的首次报道,也是在西北太平洋区的首次记录。小中喙鲸的主
要形态鉴别特征为有1 对纺锤形牙齿着生在下颌骨联合后面。经对已报道过的大陆海域搁浅和误捕的3 个雌性
银杏齿中喙鲸头骨标本和台湾省搁浅银杏齿中喙鲸的颅骨、鼻骨、下颌骨以及牙齿特征对比重新鉴定,订正大
陆的3 个样本为雌性柏氏中喙鲸。本文报道了大陆沿岸海域搁浅和误捕的喙鲸类最新调查研究结果。     

Productional characteristics of redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Scorpaeniformes,Sebastidae) in the Barents Sea and adjacent waters

The annual production of redfish Sebastes mentella of the Norway-Barents Sea population is estimated. The main contribution to the formation of production is made by specimens of the 10–15 year age and in the period of high abundance of recruitment the main contribution is by immature specimens of the 1–8 year age. The generative production of redfish is, on average, by four times lower than the somatic production. The ratio between generative and somatic production is estimated in relation to the population structure. The value of P/B coefficient is in reverse relationship with the individual age and weight. As the part of the junior age groups in the population decreases P/B coefficient increases, and with the increase of the individual average weight in the population it decreases. The relationship between the specific rate of weight growth of redfish and the value of P/B coefficient is shown. The average value of P/B coefficient for the Norway-Barents Sea population of redfish is 0.3.     

Ecologal and parasitological chracteristics of redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Scorpaeniformes: Sebastidae) from the Norwegian Sea and adjacent waters

Special traits of ecology, zoogeography, formation of fauna of parasites, and occurrence of external lesions are investigated in redfish Sebastes mentella from the Norwegian Sea and the adjacent area of the Barents Sea. A considerable weakening of connection with bottom biocenoses in redfish in the pelagial of the Norwegian Sea indicates that it lives here for most of its annual life cycle. In redfish from south of the open part of the Norwegian Sea, there are noticeable differences in the fauna of parasites and in occurrence of external lesions from those in the fish from the north and east of this sea while traits characteristic of redfish from the Irminger Sea are present.     

Color patterns in white‐beaked dolphins (Lagenorhynchus albirostris) from Iceland

Few studies have examined the natural complex pigmentation patterns of white‐beaked dolphins. From 2002 to 2014, whale‐watching trips in Iceland provided a platform of opportunity to collect a large body of photographs of free‐ranging individuals from a single area of distribution for this species. Based on 823 images, 571 individuals showing one or more color components were identified, and assigned to the following four age classes: adults (n = 437), juveniles (n = 109), calves (n = 14), and neonates (n = 11). A total of 26 color components were observed and described: seven terms previously applied to white‐beaked dolphins, 12 previously applied to other dolphin species, and seven newly defined terms. Results showed that each age class could be positively identified by differences in specific color components, some of which were exclusive. Therefore, color patterns may prove useful in estimating maturity in free‐ranging white‐beaked dolphins. This tool could be further refined through assessment of a wide sample of freshly stranded specimens of known sex and age, which could reveal new age class‐specific components, as well as sexually dimorphic characteristics not seen here. Geographic variation should be investigated by comparing image data sets and stranded animals from different parts of the North Atlantic.     

Molecular genetic identification of southern hemisphere beaked whales (Cetacea: Ziphiidae)

To assist in the species-level identification of stranded and hunted beaked whales, we compiled a database of 'reference' sequences from the mitochondrial DNA control region for 15 of the 20 described ziphiid species. Reference samples for eight species were obtained from stranded animals in New Zealand and South Australia. Sequences for a further seven species were obtained from a previously published report. This database was used to identify 20 'test' samples obtained from incompletely documented strandings around New Zealand. Analyses showed that four of these 'test' specimens (20%) had initially been misidentified. These included two animals of particular interest: (i) a Blainville's beaked whale ( Mesoplodon densirostris) , the first record of this species in New Zealand waters; and, (ii) a juvenile Andrews' beaked whale ( Mesoplodon bowdoini ), a species known from just over 20 strandings worldwide. A published sequence from a beaked whale product purchased in the Republic of Korea was identified as a Cuvier's beaked whale ( Ziphius cavirostris ). Levels of intra- and interspecific variation were compared to determine the potential for misidentification when the database or taxonomy is incomplete. Intraspecific variation was generally <2%, and interspecific divergence was generally >4.7%. Exceptions were within-species variation in Hyperoodon planifrons , southern bottlenosed whale (4.12%), which exceeded the variation between the two species of Berardius (3.78%), and variation between the two specimens assigned to M. hectori , Hector's beaked whale (7.14%). The latter case appears to be an error in species identification, and could represent the discovery of a new species of beaked whale.     

The ecological and parasitological characteristics of the golden redfish, <Emphasis Type="Italic">Sebastes norvegicus</Emphasis> (Ascanius, 1772) (Teleostei: Scorpaenidae) that inhabit the Arctic Ocean Seas

An ecological, faunistic, and zoogeographical analysis of the parasite fauna of the golden redfish Sebastes norvegicus (Ascanius, 1772) that inhabit the Barents, Norwegian, and Greenland seas, has been performed. The specifics of formation of the parasite fauna in this species have been studied.     

Genetic structure of the beaked whale genus Berardius in the North Pacific,with genetic evidence for a new species

There are two recognized species in the genus Berardius, Baird's and Arnoux's beaked whales. In Japan, whalers have traditionally recognized two forms of Baird's beaked whales, the common “slate‐gray” form and a smaller, rare “black” form. Previous comparison of mtDNA control region sequences from three black specimens to gray specimens around Japan indicated that the two forms comprise different stocks and potentially different species. We have expanded sampling to include control region haplotypes of 178 Baird's beaked whales from across their range in the North Pacific. We identified five additional specimens of the black form from the Aleutian Islands and Bering Sea, for a total of eight “black” specimens. The divergence between mtDNA haplotypes of the black and gray forms of Baird's beaked whale was greater than their divergence from the congeneric Arnoux's beaked whale found in the Southern Ocean, and similar to that observed among other congeneric beaked whale species. Taken together, genetic evidence from specimens in Japan and across the North Pacific, combined with evidence of smaller adult body size, indicate presence of an unnamed species of Berardius in the North Pacific.     

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.     

Geographic distribution of the Cross Seamount beaked whale based on acoustic detections

Beaked whales produce frequency-modulated echolocation pulses that appear to be species-specific, allowing passive acoustic monitoring to play a role in understanding spatio-temporal patterns. The Cross Seamount beaked whale is known only from its unique echolocation signal (BWC) with no confirmed species identification. This beaked whale spans the Pacific Ocean from the Mariana Archipelago to Baja California, Mexico, south to the equator, but only as far north as latitude 29°N. Within these warm waters, 92% of BWC detections occurred at night, 6% during crepuscular periods, and only 2% during daylight hours. Detections of BWC signals on drifting recorders with a vertical hydrophone array at 150 m depth demonstrated that foraging often occurred shallow in the water column (<150 m). No other species of beaked whale to date has been documented foraging in waters this shallow. Given their nocturnal, shallow foraging dives, this species appears to prefer prey that may be available in the water column only during those hours. The foraging behavior of Cross Seamount beaked whales appears to be unique among all beaked whales, and these findings contribute additional ecological and acoustic information which can help guide future efforts to identify this cryptic whale.