Ice Cod Arctogadus glacialis (Peters, 1874) in Northeast Greenland—A First Sketch of Spatial Occurrence and Abundance

Based on bottom trawl catches during the years 2002–2017, we present the first large-scale baseline on the spatial distribution and abundance of ice cod Arctogadus glacialis (Peters, 1874) in the fjords and on the shelf in Northeast Greenland (latitudes 70 °N–78 °N). Ice cod abundance peaked in the secluded sill fjords such as Bessel Fjord, Brede Fjord, Clavering Ø fjord system and Kong Oscar Fjord as compared to the offshore shelf. The mean biomass was estimated as 3.9 kg/km2 on the shelf and 49.3 kg/km2 in the fjords. Nearly 45% of the biomass was restricted to temperatures < −1.0 °C and almost 90 % of the biomass occurred within 200–600 m depth. This corresponds well with the deep, subzero fjords along the Northeast Greenland coast which, thus, appear the most suitable habitat for ice cod. Moreover, there was a gradual decrease in ice cod biomass on the shelf over the years 2002–2017. This apparent relocation of ice cod matches the ongoing warming of the Northeast Greenland shelf waters. Given that the overall temperature space of ice cod spans less than 4 ºC in Northeast Greenland, it is likely that the species is particularly vulnerable to climate change as warmer waters before long enter the fjords, i.e., the main habitat for ice cod

Approaching the Arctic: the occurrence of Parin’s spinyfin Diretmichthys parini (Beryciformes: Diretmidae) in the Nordic Seas

Two adult specimens of the tropical to subtropical fish species Diretmichthys parini are reported from the North Sea and the northern Norwegian Sea, respectively. Both were accidentally caught as bycatch by commercial trawlers. Although not uncommon in Icelandic waters, it has not been documented from the Nordic Seas previously. In light of the major currents and water temperatures in the area, this is puzzling. Whether this pattern reflects a true distributional change or increased awareness and reporting from fishermen is not known.publishedVersio

Anatomical distribution of scavenger endothelial cells in bony fishes (Osteichthyes)

The scavenger endothelial cells (SECs) of vertebrates are an important class of endocytic cells responsible for clearance of foreign and physiological waste macromolecules, partitioning in the immune system, functioning as a cellular powerplant by producing high energy metabolites like lactate and acetate. All animal phyla possess SECs, but the tissue localization of SECs has only been investigated in a limited number of species. By using a specific ligand for scavenger receptors (formalin treated bovine serum albumin), the study revealed that in all tetrapod species (amphibia, reptiles, birds and mammals) the SECs were found lining the sinusoids of the liver. No SECs were found in the liver of any of the bony fishes (Osteichthyes) investigated. Interestingly, we found the SECs not only to be located in the heart of marine species but also in some freshwater species such as Lota lota, Percichthys trucha and Perca fluviatilis. In some fish species, the SECs were found both in the heart and/or kidney in a number of marine and freshwater fishes, whereas in some marine, diadromous and freshwater fishes the SECs were confined only to the kidney tissue. However, from these results it can be suggested that there is neither a clear phylogenetic trend when it came to anatomical localization of SECs nor any pattern in terms of habitat (salinity preferences)

Assessing the reproductive biology of the Greenland shark (Somniosus microcephalus)

The Greenland shark (Somniosus microcephalus, Squaliformes: Somniosidae) is a long-lived Arctic top predator, which in combination with the high historical and modern fishing pressures, has made it subject to increased scientific focus in recent years. Key aspects of reproduction are not well known as exemplified by sparse and contradictory information e.g. on birth size and number of pups per pregnancy. This study represents the first comprehensive work on Greenland shark reproductive biology based on data from 312 specimens collected over the past 60 years. We provide guidelines quantifying reproductive parameters to assess specific maturation stages, as well as calculate body length-at-maturity (TL50) which was 2.84±0.06 m for males and 4.19±0.04 m for females. From the available information on the ovarian fecundity of Greenland sharks as well as a meta-analysis of Squaliform reproductive parameters, we estimate up to 200–324 pups per pregnancy (depending on maternal size) with a body length-at-birth of 35–45 cm. These estimates remain to be verified by future observations from gravid Greenland sharks

A holistic and comprensive data approach validates the distribution of the critically endangered flapper skate (Dipturus intermedius)

Morphological similarities between skates of the genus Dipturus in the north-eastern Atlantic and mediterranean have resulted in longstanding confusion, misidentification and misreporting. Current evidence indicates that the common skate is best explained as two species, the flapper skate (Dipturus intermedius) and the common blue skate (D. batis). However, some management and conservation initiatives developed prior to the separation continue to refer to common skate (as ‘D. batis’). This taxonomic uncertainty can lead to errors in estimating population viability, distribution range, and impact on fisheries management and conservation status. Here, we demonstrate how a concerted taxonomic approach, using molecular data and a combination of survey, angler and fisheries data, in addition to expert witness statements, can be used to build a higher resolution picture of the current distribution of D. intermedius. Collated data indicate that flapper skate has a more constrained distribution compared to the perceived distribution of the ‘common skate’, with most observations recorded from Norway and the western and northern seaboards of Ireland and Scotland, with occasional specimens from Portugal and the Azores. Overall, the revised spatial distribution of D. intermedius has significantly reduced the extant range of the species, indicating a possibly fragmented distribution range.acceptedVersio

A holistic and comprehensive data approach validates the distribution of the critically endangered flapper skate (Dipturus intermedius)

Morphological similarities between skates of the genus Dipturus in the north-eastern Atlantic and Mediterranean have resulted in longstanding confusion, misidentification and misreporting. Current evidence indicates that the common skate is best explained as two species, the flapper skate (Dipturus intermedius) and the common blue skate (D. batis). However, some management and conservation initiatives developed prior to the separation continue to refer to common skate (as ‘D. batis’). This taxonomic uncertainty can lead to errors in estimating population viability, distribution range, and impact on fisheries management and conservation status. Here, we demonstrate how a concerted taxonomic approach, using molecular data and a combination of survey, angler and fisheries data, in addition to expert witness statements, can be used to build a higher resolution picture of the current distribution of D. intermedius. Collated data indicate that flapper skate has a more constrained distribution compared to the perceived distribution of the ‘common skate’, with most observations recorded from Norway and the western and northern seaboards of Ireland and Scotland, with occasional specimens from Portugal and the Azores. Overall, the revised spatial distribution of D. intermedius has significantly reduced the extant range of the species, indicating a possibly fragmented distribution range

Identification Guide for Skates (Chondrichthyes: Rajiformes) in Norwegian waters, for both sexes and all stadiums

This document is an appendix to Arve Lynghammar's doctoral thesis which is available in Munin at http://hdl.handle.net/10037/6785</a

Chondrichthyan fishes in the Arctic Ocean and adjacent seas - do we know our species?

The basal prerequisite for managing species and understanding ecosystems is correct species and population identification. Without knowing the species, we cannot with accuracy detect changes in distribution or abundance due to climate change, fisheries, diseases or any other types of impact. This thesis gives the first complete overview of chondrichthyan fishes (sharks, skates, rays and chimaeras), recorded in the Arctic Ocean and adjacent seas. A total of 49 species were found to occur, and the most specious regions were the Bering Sea, the Norwegian Sea and the Barents Sea, also known as the Arctic Gateways. The Bering Strait is an effective zoogeographic barrier, separating the Pacific from the Atlantic species. In particular, skates are prone to misidentifications. Species complexes are known to occur, and the group is commonly lumped as “Skates & Rays” in fishery statistics or in scientific publications. By use of genetic methods (DNA barcoding), the skate species reported from the northern Northeast (nNE) Atlantic was investigated. A total of 12 species were found to occur in the area, and three of those were new for the region. Skates are commonly encountered in the nNE Atlantic, but ~95 % are the smaller-sized Amblyraja radiata. Larger skates may be landed and they are necessarily a mix of the remaining 11 species, some of which are considered threatened. There were strong indications of the disappearance of Leucoraja fullonica, as well as over-reporting of the critically endangered common skate complex formerly known as Dipturus batis. Amblyraja radiata was suspected to be cryptic due to large differences in size-at-maturity across its distributional range. However, the mitochondrial gene cytochrome c oxidase subunit 1 (COI) did not support this hypothesis. To further elucidate this question, a higher resolution method was applied, and 10 microsatellite markers were investigated from specimens across the North (N) Atlantic. Pairwise fixation indexes (FST) indicated that there may be three major clusters in the N Atlantic: Northwest Atlantic, Mid Atlantic (Greenland) and NE Atlantic. However, more rigorous tests revealed high physical mixing of individuals over a large geographical area. The microsatellite results did not support the hypothesis of A. radiata being cryptic. Although the population structure of A. radiata could not be fully explained, baselines for occurrence of chondrichthyan fishes are established, and a new identification guide for skates in the nNE Atlantic is provided. Hopefully, this will pave the way for a better management of the skates by improving data quality

Approaching the Arctic: the occurrence of Parin’s spinyfin Diretmichthys parini (Beryciformes: Diretmidae) in the Nordic Seas

Two adult specimens of the tropical to subtropical fish species Diretmichthys parini are reported from the North Sea and the northern Norwegian Sea, respectively. Both were accidentally caught as bycatch by commercial trawlers. Although not uncommon in Icelandic waters, it has not been documented from the Nordic Seas previously. In light of the major currents and water temperatures in the area, this is puzzling. Whether this pattern reflects a true distributional change or increased awareness and reporting from fishermen is not known

Approaching the Arctic: the occurrence of Parin’s spinyfin Diretmichthys parini (Beryciformes: Diretmidae) in the Nordic Seas

Two adult specimens of the tropical to subtropical fish species Diretmichthys parini are reported from the North Sea and the northern Norwegian Sea, respectively. Both were accidentally caught as bycatch by commercial trawlers. Although not uncommon in Icelandic waters, it has not been documented from the Nordic Seas previously. In light of the major currents and water temperatures in the area, this is puzzling. Whether this pattern reflects a true distributional change or increased awareness and reporting from fishermen is not known