Non-lethal sampling of juvenile herring

PROJECT

Non-lethal Sampling of Juvenile Herring

Background


To estimate the biomass of various fish acoustic surveys are preformed.  Unfortunately, the acoustic systems cannot identify the fish length or species needed to convert the acoustic signal to a biomass estimate.  Currently various methods are used to capture fish to gain that information.  Advances in imaging sonar and camera systems may provide a means to collect the necessary information without needing to kill the fish.  Deploying those systems on a remotely operated vehicle also offers a way to get closer to shore and under ice to examine if juvenile herring are using habitats we cannot survey by traditional means.

Methods

A Didson imaging sonar is integrated onto a remotely operated vehicle that has a video camera and lights.  The imaging sonar allows researcher’s to observe the fish beyond the range of the camera and it can be used to calculate fish measurements.  The system is then deployed to investigate schools of fish as directed from the acoustic survey or used to search for fish under the sea ice.  When fish are found using the acoustics the ROV is then driven closer to allow the fish to be observed in the camera to help identify the species.

What we will learn

This project will demonstrate if it is possible to collect the data needed to complete the interpretation of acoustic survey data without needing to kill the fish being observed.  It will also show if juvenile herring are utilizing ice cover on fjords as a habitat.  The presumption being that they would be using this habitat to allow feeding near the surface without predation by birds.