TY - JOUR
T1 - Visual surveys can reveal rather different 'pictures' of fish densities
T2 - Comparison of trawl and video camera surveys in the Rockall Bank, NE Atlantic Ocean
AU - McIntyre, F. D.
AU - Neat, F.
AU - Collie, N.
AU - Stewart, M.
AU - Fernandes, P. G.
N1 - Funding Information:
This work received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (Grant reference HR09011 ) and contributing institutions. Thanks to Marine Scotland Science and the cruise leaders of the anglerfish surveys including all the crew.
Publisher Copyright:
© 2014 Elsevier Ltd.
PY - 2015/1
Y1 - 2015/1
N2 - Visual surveys allow non-invasive sampling of organisms in the marine environment which is of particular importance in deep-sea habitats that are vulnerable to damage caused by destructive sampling devices such as bottom trawls. To enable visual surveying at depths greater than 200m we used a deep towed video camera system, to survey large areas around the Rockall Bank in the North East Atlantic. The area of seabed sampled was similar to that sampled by a bottom trawl, enabling samples from the towed video camera system to be compared with trawl sampling to quantitatively assess the numerical density of deep-water fish populations. The two survey methods provided different results for certain fish taxa and comparable results for others. Fish that exhibited a detectable avoidance behaviour to the towed video camera system, such as the Chimaeridae, resulted in mean density estimates that were significantly lower (121fish/km2) than those determined by trawl sampling (839fish/km2). On the other hand, skates and rays showed no reaction to the lights in the towed body of the camera system, and mean density estimates of these were an order of magnitude higher (64fish/km2) than the trawl (5fish/km2). This is probably because these fish can pass under the footrope of the trawl due to their flat body shape lying close to the seabed but are easily detected by the benign towed video camera system. For other species, such as Molva sp, estimates of mean density were comparable between the two survey methods (towed camera, 62fish/km2; trawl, 73fish/km2). The towed video camera system presented here can be used as an alternative benign method for providing indices of abundance for species such as ling in areas closed to trawling, or for those fish that are poorly monitored by trawl surveying in any area, such as the skates and rays.
AB - Visual surveys allow non-invasive sampling of organisms in the marine environment which is of particular importance in deep-sea habitats that are vulnerable to damage caused by destructive sampling devices such as bottom trawls. To enable visual surveying at depths greater than 200m we used a deep towed video camera system, to survey large areas around the Rockall Bank in the North East Atlantic. The area of seabed sampled was similar to that sampled by a bottom trawl, enabling samples from the towed video camera system to be compared with trawl sampling to quantitatively assess the numerical density of deep-water fish populations. The two survey methods provided different results for certain fish taxa and comparable results for others. Fish that exhibited a detectable avoidance behaviour to the towed video camera system, such as the Chimaeridae, resulted in mean density estimates that were significantly lower (121fish/km2) than those determined by trawl sampling (839fish/km2). On the other hand, skates and rays showed no reaction to the lights in the towed body of the camera system, and mean density estimates of these were an order of magnitude higher (64fish/km2) than the trawl (5fish/km2). This is probably because these fish can pass under the footrope of the trawl due to their flat body shape lying close to the seabed but are easily detected by the benign towed video camera system. For other species, such as Molva sp, estimates of mean density were comparable between the two survey methods (towed camera, 62fish/km2; trawl, 73fish/km2). The towed video camera system presented here can be used as an alternative benign method for providing indices of abundance for species such as ling in areas closed to trawling, or for those fish that are poorly monitored by trawl surveying in any area, such as the skates and rays.
KW - Behaviour
KW - Deep-water
KW - Towed camera
KW - Visual survey
UR - http://www.scopus.com/inward/record.url?scp=84911059145&partnerID=8YFLogxK
U2 - 10.1016/j.dsr.2014.09.005
DO - 10.1016/j.dsr.2014.09.005
M3 - Article
AN - SCOPUS:84911059145
SN - 0967-0637
VL - 95
SP - 67
EP - 74
JO - Deep-Sea Research Part I: Oceanographic Research Papers
JF - Deep-Sea Research Part I: Oceanographic Research Papers
ER -
