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Prawn spawner index in Howe Sound, BC

Learn about how we study changes in prawn populations on the Pacific coast.


Prawn spawner index in Howe Sound, BC

My name is Ken Fong.

I'm the head of the Marine Invertebrates Section at the Pacific Biological Station here in Nanaimo with Fisheries and Oceans Canada.

The prawn surveys that we do are conducted in Howe Sound.

We do surveys in February and we do surveys in November.

We established this area since 1985, and we've been surveying it since, so we can understand how prawn populations have changed over time, or if there are changes of prawn populations over time.

So we want to know: how many males are out there, how many transitions, how many females, how many females with eggs, and how many females have already spawned.

With a trained eye, we can identify whether it's a male, it's in a transition, or it's female stage.

The unique things about prawns is that they have a very unique life cycle, where they generally start off as males and change their sex halfway through their life into females.

After we sort the catch, we take the 200 prawn samples down into the lab of the ship.

We have a number of sampling stations down below; we have a computer where we enter, and calipers where we measure the prawn; we have a motion compensated scale where we weigh each individual prawn - it can weigh them down to 1/2 a gram, and we have a database where once we measure the prawn.

We enter that information into that database.

We're always very interested in knowing that there's changes in not only the different types of species that we're catching but also if there's changes in the prawns, whether or not they're getting smaller or they're getting bigger, and we're always very excited to go out and see what we're going to encounter next.

As biologist and scientists this really makes our job fun.

DFO scientists analyze the data for spawner index which is the number of females per trap and we provide that advice or information to fisheries managers so that they can make decisions on whether or not to keep an area open for fishing or to close an area for fishing.

So it's very important for Canadians, when they're out fishing for prawns, to release those females with eggs back in the water so that we can ensure that future generations of Canadians can go out and fish for prawns.
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