Wednesday, August 24, 2011

Montreal Expedition: Working with wolffish

New England Aquarium researchers are reporting from the Biodôme in Montréal, Quebec, where they are conducting an experiment on the stress physiology of two species of wolffish.

Working with wolffish is challenging and exciting. These large, feisty fish definitely keep you on your toes. They have a lot of personality to go along with their sharp teeth and if they are hungry, they can be a bit grumpy. This is one of the reasons we sedate the fish before taking blood samples from them; working with a sleeping wolffish reduces the risk of injury to both the researcher and the animal.

This Atlantic wolffish, on exhibit at the Biodome, even recognizes the aquarist who brings food and can pick him out of a crowd. These fish are definitely intelligent!

A wide, one-toothed smile from one of the spotted wolffish.

One of the most interesting aspects of the project has been observing the very different behavior of the two species we are studying. While the spotted wolffish (A. minor) tend to be more docile, the Atlantic wolffish (A. lupus) are much more active and aggressive. For example, since these fish prefer to shelter under rocky outcroppings in the wild, we provided all the tanks with structures for the fish to hide in. These plastic structures were weighted down with fishing weights. Whether it was because they resented the decoration or thought that the shiny silver weights looked like tasty fish, within a few days the Atlantic wolffish had chewed many of the weights right off of the bottom of their shelters. The spotted wolffish, on the other hand, left the weights on their shelters alone.

 Both species of wolffish liked to hide in and around these structures, 
but only the Altantic wolffish bit the silver weights holding them down.

Members of the Atlantic species will also swim right to the surface when you lift the lid in their tank, especially if they want to be fed. All those teeth coming at you can be very intimidating!

Hope’s teeth aren’t quite as scary as those of the Altantic wolffish she is holding.

The fish aren’t always friendly towards each other either. Most of the animals bear scars from the sharp teeth of their tankmates. Members of the Atlantic species are definitely more scarred than members of the spotted species, indicating higher aggression levels.

 This Atlantic wolffish has a huge gash under its eye from one of its cohorts.

One of our coolest wolffish experiences was stripping eggs from a couple of pregnant female Atlantic wolffish. Some of the females were heavily pregnant and if these animals are stressed, they are sometimes unable to release the eggs, which can endanger the health of the animal. To prevent this, while the pregnant females were asleep, we massaged their abdomens from head to tail to push the eggs out; this is known as “stripping” the animals. It took about 20 minutes for us to strip all of the eggs and by the end we had removed about 400g of eggs from each female, roughly one fifth of their body weight!

On the left, the very fat belly of a pregnant female Atlantic wolffish and on the right, 
we squeeze eggs from a sedated Atlantic wolffish female.

Although they are not perhaps the most cute and cuddly of creatures, by the end of our Biodome experience, all three of us felt a lot of affection for our wolffish friends!

The three of us (left to right: Hope, Alena and Emily) with our fishy friends.

- Emily Jones

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