Young Fish Provide Clues to Future Pacific Cod Stock Size - Post 3

August 03, 2018

Learn how baited cameras are used to survey fish populations.

Age-1 Pacific cod are much larger (15-20 cm) and are more common at deeper depths. This set was deployed along at 10 m.

Age-1 Pacific cod are much larger (15-20 cm) and are more common at deeper depths. This set was deployed along at 10 m.

Alaska is not renowned for its good weather but there are exceptions!

Alaska is not renowned for its good weather but there are exceptions!

Older age classes of fish (age-1s) are still resident in the nearshore embayments around Kodiak Island, but they are tricky to sample-----they’re generally too deep for the seine and too shallow for trawl nets.   We also want to be careful not to harm sensitive habitat types (boulders, reefs, macroalgae) where these small fish live.

Enter the ‘baited camera.’

Baited cameras have been in use around the world, especially around fragile tropical reef areas. Our research team has been using underwater cameras to survey juvenile Pacific cod since 2006, and they will continue to be a valuable tool for tracking cohorts of juvenile fish in coastal nurseries.

baited cameras

Here is one of a set of identical baited cameras we are using this summer in Kodiak, AK.  The lightweight aluminum frames and autonomous cameras allow us to deploy multiple cameras at once before retrieval.

Two size groups of juvenile Pacific cod generally approach the bait bag---age-0 fish (insert figure 1 image here) and age-1 fish (insert Fig 3).   Scientists determine what age group an approaching fish fits into based on their relative size compared to the bait box and parallel supporting bars.

Cameras are deployed for 15-minute periods and then hauled back and redeployed at another site further away. Data gathered in this type of survey do not provide true counts of fish in an area, but allow us to analyze relative trends in abundance and habitat use.

Age-0 Pacific cod are smaller (5-9 cm) and generally restricted to shallow depths.

Age-0 Pacific cod are smaller (5-9 cm) and generally restricted to shallow depths.  This set was deployed along the 3 m depth contour.

We’ll be back in August to conduct more baited camera surveys of the same region and will expand the survey to other parts of Alaska in 2019.

Meet the Blogger

Young_Fish_Provide_Clues_to_Future_Pacific_Cod-IMAGE1.jpg

Ben Laurel, Alaska Fisheries Science Center.

Ben Laurel has more than 20 years of experience studying early life stages of cold-water commercial fish species. He currently leads several field and laboratory research projects involving graduate students and technical staff at the Alaska Fisheries Science Center lab in Newport, Oregon. Ben began his science career as graduate student in Newfoundland, Canada following the collapse of the Atlantic cod fishery. He now is very interested in Pacific cod and how this species is responding to rapidly changing environmental conditions in Alaskan waters.

In his free time, Ben and his family love to adventure in Oregon and Alaska.