Cruise inventory

FRV Explorer 4/81

Cruise summary report

Cruise Info. 
Ship name (ship code)FRV Explorer (74EX)
Cruise identifier4/81
Cruise period1981-05-20 — 1981-05-29
StatusCompleted
Port of departureAberdeen, United Kingdom
Port of returnAberdeen, United Kingdom
PurposeResearch
Objectives1. To carry out a bottom trawling survey in the northern North Sea and to the north of Scotland to determine the effect and distribution of infection of two diseases, Ichthyophonus and Lernaeocera in haddock and Ichthyophonus in plaice.
2. To carry out an echo survey for herring in the Shetland area.
3. To sample pure North Sea stocks of mackerel for biological tag studies.
4. To sample gadoids from the vicinity of oil fields and remotely for oil degrading enzyme analysis.
5. To carry out experimental studies on post mortem migration of larval Anisakis.
6. Tagging trials with a new dogfish tag.
7. To sample gadoid stomachs from selected stations for food analysis.

26 Stations were worked throughout the cruise. Samples of juvenile lemon sole were preserved for early determination of Lernaeocera. Experiments were done to investigate reasons for the mass migration of Anisakis. Gadoid stomach samples were taken and preserved for subsequent food analysis. Skin ulceration in Limand limanda were recorded. Bacteriological cultures were made for laboratory identification of infectious organisms. Parasite samples from various species of fish were taken from all hauls for ecological and taxonomic studies.
Chief scientistA H McVicar (Department of Agriculture and Fisheries for Scotland Aberdeen Marine Laboratory)
Cruise reportFRV Explorer 4/81 cruise report explorer4_81.pdf — access key 'C' (1.14 MB) 
Ocean/sea areas 
GeneralNorth Sea
Norwegian Sea
North East Atlantic Ocean (limit 40W)
SpecificN. North Sea, Beryl Oil Field, Fair Isle, W of Orkney, Moray Firth, Scalloway Deeps
Track chartsFRV Explorer 4/81 cruise track — explorer4_81track.pdf (00 MB) 
Measurements 
Biology and fisheries 
Pelagic fishQuantity: number of hauls = 9
Description: pathology studies. 1150 haddock were examined for Lernaeocera and samples of kidney removed for microscopic determination of Ichthyophonus. 92 plaice were examined for Ichthyophonus. Gel diffusion tests were carried out on all plaice and 50 haddock. 350 mackerel were sampled for biological tag studies. 224 squalus and 79 Scyliorhinus were double tagged and released.
Demersal fishQuantity: number of hauls = 9
Description: pathology studies. 1150 haddock were examined for Lernaeocera and samples of kidney removed for microscopic determination of Ichthyophonus. 92 plaice were examined for Ichthyophonus. Gel diffusion tests were carried out on all plaice and 50 haddock. 350 mackerel were sampled for biological tag studies. 224 squalus and 79 Scyliorhinus were double tagged and released.
TaggingsQuantity: number of hauls = 9
Description: pathology studies. 1150 haddock were examined for Lernaeocera and samples of kidney removed for microscopic determination of Ichthyophonus. 92 plaice were examined for Ichthyophonus. Gel diffusion tests were carried out on all plaice and 50 haddock. 350 mackerel were sampled for biological tag studies. 224 squalus and 79 Scyliorhinus were double tagged and released.
Other biological/fisheries measurementQuantity: number of hauls = 12
Description: arylhydrocarbon hydroxylase enzyme analysis. Samples of liver homogenate frozen in liquid nitrogen for enzyme analysis and fixed pyloric caeca for pancreas histology were taken from 29 cod, 64 whiting and 65 haddock