Limits...
Deep vision: an in-trawl stereo camera makes a step forward in monitoring the pelagic community.

Underwood MJ, Rosen S, EngΓ₯s A, Eriksen E - PLoS ONE (2014)

Bottom Line: The system showed potential for measuring the length of small organisms and also recorded the vertical and horizontal positions where individuals were imaged.Young-of-the-year fish were difficult to identify when passing the camera at maximum range and to quantify during high densities.This study suggests modifications to the Deep Vision and the trawl to increase our understanding of the population dynamics.

View Article: PubMed Central - PubMed

Affiliation: Institute of Marine Research, Bergen, Norway; Department of Biology, University of Bergen, Bergen, Norway.

ABSTRACT
Ecosystem surveys are carried out annually in the Barents Sea by Russia and Norway to monitor the spatial distribution of ecosystem components and to study population dynamics. One component of the survey is mapping the upper pelagic zone using a trawl towed at several depths. However, the current technique with a single codend does not provide fine-scale spatial data needed to directly study species overlaps. An in-trawl camera system, Deep Vision, was mounted in front of the codend in order to acquire continuous images of all organisms passing. It was possible to identify and quantify of most young-of-the-year fish (e.g. Gadus morhua, Boreogadus saida and Reinhardtius hippoglossoides) and zooplankton, including Ctenophora, which are usually damaged in the codend. The system showed potential for measuring the length of small organisms and also recorded the vertical and horizontal positions where individuals were imaged. Young-of-the-year fish were difficult to identify when passing the camera at maximum range and to quantify during high densities. In addition, a large number of fish with damaged opercula were observed passing the Deep Vision camera during heaving; suggesting individuals had become entangled in meshes farther forward in the trawl. This indicates that unknown numbers of fish are probably lost in forward sections of the trawl and that the heaving procedure may influence the number of fish entering the codend, with implications for abundance indices and understanding population dynamics. This study suggests modifications to the Deep Vision and the trawl to increase our understanding of the population dynamics.

Show MeSH

Related in: MedlinePlus

Length comparison of polar cod (Boreogadus saida) measured by two different methods.The dark column bars indicate measurements from the Deep Vision data (nβ€Š=β€Š77, mean β€Š=β€Š34 mm), while the catch data measurements are indicated by white column bars (nβ€Š=β€Š50, mean β€Š=β€Š34 mm).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4230979&req=5

pone-0112304-g007: Length comparison of polar cod (Boreogadus saida) measured by two different methods.The dark column bars indicate measurements from the Deep Vision data (nβ€Š=β€Š77, mean β€Š=β€Š34 mm), while the catch data measurements are indicated by white column bars (nβ€Š=β€Š50, mean β€Š=β€Š34 mm).

Mentions: Fifty polar cod were measured from the catch and 77 out of 115 individuals were measured from the images for length comparisons (the remaining 38 were not imaged in orientations where lengths could be estimated). Average lengths of polar cod were not significantly different in the images and catch data (mean length 34 mm for each method; Fβ€Š=β€Š0.034, pβ€Š=β€Š0.85; Fig. 7). The single Northeast Arctic cod was measured at 53 mm in both the Deep Vision image and the catch data. Only the larger of the two shorthorn sculpin was passed in an orientation where it could be measured. Its length was calculated to be 43 mm in the Deep Vision image compared to 45 mm in the catch data (4.4% difference).


Deep vision: an in-trawl stereo camera makes a step forward in monitoring the pelagic community.

Underwood MJ, Rosen S, EngΓ₯s A, Eriksen E - PLoS ONE (2014)

Length comparison of polar cod (Boreogadus saida) measured by two different methods.The dark column bars indicate measurements from the Deep Vision data (nβ€Š=β€Š77, mean β€Š=β€Š34 mm), while the catch data measurements are indicated by white column bars (nβ€Š=β€Š50, mean β€Š=β€Š34 mm).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230979&req=5

pone-0112304-g007: Length comparison of polar cod (Boreogadus saida) measured by two different methods.The dark column bars indicate measurements from the Deep Vision data (nβ€Š=β€Š77, mean β€Š=β€Š34 mm), while the catch data measurements are indicated by white column bars (nβ€Š=β€Š50, mean β€Š=β€Š34 mm).
Mentions: Fifty polar cod were measured from the catch and 77 out of 115 individuals were measured from the images for length comparisons (the remaining 38 were not imaged in orientations where lengths could be estimated). Average lengths of polar cod were not significantly different in the images and catch data (mean length 34 mm for each method; Fβ€Š=β€Š0.034, pβ€Š=β€Š0.85; Fig. 7). The single Northeast Arctic cod was measured at 53 mm in both the Deep Vision image and the catch data. Only the larger of the two shorthorn sculpin was passed in an orientation where it could be measured. Its length was calculated to be 43 mm in the Deep Vision image compared to 45 mm in the catch data (4.4% difference).

Bottom Line: The system showed potential for measuring the length of small organisms and also recorded the vertical and horizontal positions where individuals were imaged.Young-of-the-year fish were difficult to identify when passing the camera at maximum range and to quantify during high densities.This study suggests modifications to the Deep Vision and the trawl to increase our understanding of the population dynamics.

View Article: PubMed Central - PubMed

Affiliation: Institute of Marine Research, Bergen, Norway; Department of Biology, University of Bergen, Bergen, Norway.

ABSTRACT
Ecosystem surveys are carried out annually in the Barents Sea by Russia and Norway to monitor the spatial distribution of ecosystem components and to study population dynamics. One component of the survey is mapping the upper pelagic zone using a trawl towed at several depths. However, the current technique with a single codend does not provide fine-scale spatial data needed to directly study species overlaps. An in-trawl camera system, Deep Vision, was mounted in front of the codend in order to acquire continuous images of all organisms passing. It was possible to identify and quantify of most young-of-the-year fish (e.g. Gadus morhua, Boreogadus saida and Reinhardtius hippoglossoides) and zooplankton, including Ctenophora, which are usually damaged in the codend. The system showed potential for measuring the length of small organisms and also recorded the vertical and horizontal positions where individuals were imaged. Young-of-the-year fish were difficult to identify when passing the camera at maximum range and to quantify during high densities. In addition, a large number of fish with damaged opercula were observed passing the Deep Vision camera during heaving; suggesting individuals had become entangled in meshes farther forward in the trawl. This indicates that unknown numbers of fish are probably lost in forward sections of the trawl and that the heaving procedure may influence the number of fish entering the codend, with implications for abundance indices and understanding population dynamics. This study suggests modifications to the Deep Vision and the trawl to increase our understanding of the population dynamics.

Show MeSH
Related in: MedlinePlus