Maritimes 4VSW Research Vessel Surveys

Study Extent

“4VSW” missions focus on the eastern half of the Scotian Shelf, and occur primarily in March, but sets in both February, and April are also present in the data.

Sampling

Collected data includes total catch in numbers and weights by species. Length frequency data is available for most species, as are the age, sex, maturity and weight information for a subset of the individual animals. When a trawl is hauled, all of the individuals are sorted baskets by species, and the baskets are weighed to get total biomass for a species.
If we have a large catch, some baskets will be kept for detailed sampling and others will be discarded. Only a subset of these are individually weighed, thus there are some occurrences which have a length but no weight. When a trawl is hauled, all of the individuals for a given species are weighed and counted. These values become total biomass and individual count. For huge catches, the individual count is sometimes calculated from the weight. Prior to 1995, they used a spring scale for measuring total weight for a species. It recorded to the nearest kg. Small catches were entered as zero. For many species, you can see Zero as the biomass estimate throughout these years.
Prior to 2005, there are some invertebrate records, but the focus was primarily on commercial species (e.g. scallop, lobster).
The “Strong Effect” shows up in the mid-90’s when Mike Strong insisted they start sorting the sculpins and pouts more carefully and our species count went up. The standard ID guide used is Scott and Scott, Atlantic fishes of Canada, and it appeared in the late 1980’s. The guide available prior to that did not distinguish between Red Hake and White Hake. We can see this in our data. There are inconsistencies in using a separate code for Red Hake before about 1978. It does not have much impact on White Hake, which has a much higher biomass, but it does for Red Hake.
Below 40cm, winter and little skate ID is questionable.

Quality Control

Data are input while at sea using the in-house developed application Groundfish Entry System. Rigorous error checks and warnings are applied and edits take place during sampling in most cases. Further quality assurance checks are applied before loading to the production database. Scientific names associated with resource occurrence records have been mapped to recognized standards - marine taxa have been mapped to the World Register of Marine Species (WoRMS). The WoRMS codes, the AphiaIDs have been included as LSIDs in the occurrence record DwC field scientificNameID.

Method steps

1. To prepare this dataset for OBIS Canada publication, data was structured into an OBIS-compatible format using R and laid out in four tables: an Event Core, Occurrence Core and three Extended Measurement of Fact extensions. Defined vocabularies listed on the Natural Environment Research Council (NERC) Vocabulary Server (NVS) were used whenever possible. Taxon matches were obtained from WoRMS.

1. Actinopterygii
   common name: Ray-finned fishes rank: class
2. Anthozoa
   common name: Sea anemones/Stony Corals/Soft corals rank: class
3. Ascidiacea
   common name: Ascidians/Tunicates/Sea Squirts rank: class
4. Asteroidea
   common name: Sea Stars rank: class
5. Bivalvia
   common name: Bivalve molluscs rank: class
6. Cephalopoda
   common name: Cephalopods rank: class
7. Demospongiae
   common name: Sponges rank: class
8. Echinoidea
   common name: Sea Urchins rank: class
9. Elasmobranchii
   common name: Sharks/Rays/Skates/etc. rank: class
10. Gastropoda
    common name: Snails rank: class
11. Hexactinellida
    common name: Hexactinellid sponges rank: class
12. Hexanauplia
    common name: Copepods/Barnacles/etc. rank: class
13. Holothuroidea
    common name: Sea cucumbers rank: class
14. Malacostraca
    common name: Crabs/Lobsters/Shrimp/Amphipods/Isopods/etc. rank: class
15. Mammalia
    common name: Mammals rank: class
16. Myxini
    common name: Hagfish rank: class
17. Ophiuroidea
    common name: Brittlestars/Basketstars/etc. rank: class
18. Petromyzonti
    common name: Lamprey rank: class
19. Polychaeta
    common name: Bristleworms/Polychaetes rank: class
20. Polyplacophora
    common name: Chitons rank: class
21. Pycnogonida
    common name: Sea Spiders rank: class
22. Scyphozoa
    common name: True jellies rank: class
23. Chordata
    common name: Chordates rank: phylum
24. Brachiopoda
    common name: Lampshells rank: phylum
25. Arthropoda
    common name: Crustaceans rank: phylum
26. Ctenophora
    common name: Comb Jellies rank: phylum
27. Porifera
    common name: Sponges rank: phylum
28. Annelida
    common name: Segmented worms rank: phylum
29. Mollusca
    common name: Molluscs rank: phylum
30. Bryozoa
    common name: Bryozoans rank: phylum

“4VSW” missions focus on the eastern half of the Scotian Shelf