Monitoring of Polycyclic Aromatic Hydrocarbons (PAHs) in Scottish Deepwater environments.

Polycyclic aromatic hydrocarbons (PAHs) were measured in environmental samples (sponges, fish and sediment) collected in 2014 and 2016 from the Faroe-Shetland Channel and Rosemary Bank Seamount. These data could be used to provide a baseline against which any changes can be assessed in the event of an oil spill and contribute to any environmental impact assessment. Concentrations in all samples were low, often below the detection limits, and were typical of reference sites. Sponges can be used as an alternative indicator species to mussels for monitoring PAHs in the marine environment as they can accumulate PAHs from both the dissolved and particulate phase. PAH concentrations in marine sponges from Scottish waters have not previously been reported. Concentrations were low, but contained a higher proportion of heavier 4- to 6-ring PAHs compared to the fish samples.

Assessing ecological and molecular divergence between the closely related species Hydrolagus pallidus and H. affinis (Chimaeridae).

This study investigated taxonomic validity of the pale ghost shark Hydrolagus pallidus Hardy & Stehmann, 1990, which was described as a species distinct from the smalleyed rabbitfish H. affinis (de Brito Capello 1868). While few morphological characters distinguish the two taxa, a striking difference in sex ratio and fixed differences (1·1-1·6% divergence) in the cytochrome oxidase subunit I barcoding gene support the recognition of both species.

Aggregating behaviour, social interactions and possible spawning in the deep-water fish Coryphaenoides rupestris.

A dense aggregation of the roundnose grenadier Coryphaenoides rupestris was observed with a towed camera at a depth of 1500 m in the Rockall Trough during September. The density of fish was 100 times greater than other sites. Within the aggregation the fish showed directional alignment, rapid swimming actions, mid-water swimming and social interactions similar to those associated with spawning in other Gadiformes.

The diversity, distribution and status of deep-water elasmobranchs in the Rockall Trough, north-east Atlantic Ocean.

Data from a scientific deep-water trawl fisheries survey in the north-east Atlantic were analysed to determine the spatial and bathymetric distribution of elasmobranch species and assess the change in relative abundance over the period 1998-2013. During this period, commercial fisheries for deep-water sharks went from being entirely unregulated, to being briefly managed, to being completely prohibited. A total of 22 species of shark and 10 species of skate were recorded between depths of 300 and 2030 m. All showed strong species-specific depth-related trends in abundance. Out of the 11 more common species, five showed no change in relative abundance over time, two (Centrophorus squamosus and Centroselachus crepidater) declined significantly and four increased in relative abundance (Apristurus aphyodes, Apristurus microps, Galeus melastomus and Deania calcea). Assuming these populations were depleted by fisheries in the past, the current data do not suggest there has been an overall recovery. Positive signs for some species in the most recent years suggest movement or recruitment back into the area; however, it is of concern that two species continued to decline. There is a continued need to have precautionary management of these elasmobranch species, and the current ban on landing these species in European waters remains appropriate.

Proliferation of elongate fishes in the deep sea.

It was hypothesized that energetically efficient anguilliform swimming and axial elongation in fishes is favoured in the deep sea and predicted that the degree of elongation of the body form of fishes would increase with depth. An index of fish shape was derived from the relationship between length and mass. This was combined with data on abundance of c. 266 fish species from 389 research trawl tows made at depths of between 300 and 2030 m in the north-east Atlantic Ocean. The degree of elongation of the fish increased with depth to c. 1250 m before levelling off. The strength of this phenomenon varied between higher level taxa, being most apparent in the Gadiformes and Osmeriformes, and weak or absent in the Perciformes and Selachimorpha. The advantage of efficient elongate body forms may explain why certain taxa such as the grenadiers (Macrouridae) have dominated the deep sea, some have restricted depth ranges, e.g. the sharks, skates and rays, and others are almost entirely absent, e.g. the flatfishes (Pleuronectiformes).

Analysing migrations of Atlantic cod Gadus morhua in the north-east Atlantic Ocean: then, now and the future.

The application of data storage tags bears the potential for a quantum leap in the research on fish migrations, because not only first-capture and recapture positions are known, but at least theoretically, the migration path during the period at large can be reconstructed. Position, however, cannot be measured directly but has to be estimated using the available data on light, temperature, pressure and salinity. The reconstructed locations based on advanced estimation techniques have been termed geolocations. Examples are discussed which illustrate the applicability of geolocations in individual path descriptions, separation of reproductively isolated populations, timing and areas of spawning, tidal transport and use of protected areas. The examples are based on archival tag data from the North Sea, the Baltic Sea, the Barents Sea and Faroese and Icelandic Waters. Besides presenting the state-of-the-art geolocations for cod Gadus morhua in the north-east Atlantic Ocean, the major aim of this review is to raise awareness of gaps in knowledge and to identify ideas for new research.

Electronic tags reveal behaviour of captured and discarded fish.

Internally implanted data storage tags (DST) recording hydrostatic pressure (depth) and temperature in Atlantic cod Gadus morhua were used to track the behaviour of nine individuals during fishing operations. Gadus morhua showed identifiable and characteristic behavioural responses to different capture processes. In a unique observation, one fish survived being discarded and upon return to the seabed exhibited a cessation of activity comparable to observations on stressed fish under laboratory conditions.

Thermal evolution of growth efficiency in Drosophila melanogaster.

Drosophila melanogaster shows geographic clines in body size, with genetically larger flies being found further from the equator and at higher altitudes. In the laboratory, evolution at lower temperatures results in genetically larger flies, and development at low temperature increases adult body size. This study demonstrates that when newly hatched larvae from laboratory temperature selection lines were raised on fixed amounts of food (yeast) at the same temperature, larvae from the lines with the cold evolutionary history required less food to produce a given size of adult. Larvae from both high- and low-temperature selection lines required more food, however, to make a given size of adult when grown in the cold than when grown in the hot. The opposite associations between growth efficiency and adult body size seen with evolution or development at low temperature are puzzling, and suggest that different mechanisms may underlie the size changes. Since environmental and evolutionary effects of temperature on body size seem to be widespread among ectotherms, some basic aspects of thermal physiology must be involved.