Fish Files 3

Fish Files in your Backyard

Northern bluefin Tuna (Thunnus thynnus)

Where do I live?

I am a native species to the western and eastern Atlantic Ocean, as well as the Mediterranean and Black Sea. There is even a subpopulation off the coast of South Africa. I am a highly migratory species of fish and swim great distances. I swim in the pelagic (pe-lag-ic) zone. This means I am a fish that swims near the surface, and not the bottom of the ocean.

What do I look like?

I am one of the largest tuna species. My body is very deep but flat from side to side. I have a shimmering metallic blue coloured body, and a silvery-white underside. My body tapers towards the end and connects to a sickle shaped tail that is very powerful. I have two dorsal fins, the first being a yellow or blue and the second, taller dorsal fin is reddish-brown. Following my second dorsal fin are 7-10 smaller finlets that are yellow with a black edge. These run down the top and bottom of my body towards my tail.

What do I eat?

My speed allows me to eat faster moving schooling fish such as anchovies, but when I am swimming slowly I will hold my mouth open to catch squid and red crab.

What is unique about me?

I am a slow growing species and can live up to 30 years. We do school together but only with other bluefin tuna the same size. It is not uncommon to see us schooling however with other species of tuna.

We are special fish too, in that we use thermoregulation (ther-mo-reg-u-la-tion). We have a special system of blood vessels that prevent any heat created through our physical activity to be lost to the surrounding water. This allows us to swim in cooler water than other fish.

How Common am I?

It is hard to say because scientists are still trying to figure out how large the Northern Bluefin population is. I am a very popular fish with both sport fisherman and the commercial fishing industry. I am very popular in the Japanese sushi market and people pay a lot of money for me. There are limits on how many of me can be caught, but it is believed that these limits are not being respected and massive over fishing is happening. This could some day, if not managed properly, lead to the collapse of the population.

Northern Pike (Esox lucius)

Where do I live?

I can be found throughout the northern parts of the globe. You can find me all over the United States and Canada, and can even be found in Russia and Europe. I tend to live near the bottom of slow moving streams, shallow weedy lakes, and cold, clear rocky water. It is here I wait to ambush my prey.

What do I look like?

I have a large flat duck-bill shaped snout. My mouth is large and lined with many large sharp teeth. My dorsal and anal fin are found far back on my long, round body. I am typically a olive green colour with rows of yellow, bean-shaped spots and a yellow to white belly. My fins will have a few or many dark spots. I can get rather large, reaching sizes up to 150cm (59 inches) and weights up to 25 kilograms (55 pounds).

What do I eat?

As a juvenile I can be cannibalistic and eat other pike.  As an adult Pike, my diet consists mostly of fish, but I have been known to eat frogs and crayfish.

What is unique about me?

I have large sensory pores on my head and the underside of my lower jaw. This is part of my lateral line system that I use to sense changes in the water and to catch my moving prey. I have a habit of catching my prey sideways in my mouth. This immobilizes the fish with my sharp teeth. I then turn my prey head first to swallow. My aggressive behaviour can be seen as harmful in some areas that I have been introduced to because I can harm other fish populations like wild salmon.

How common am I?

I am a popular sport fish that can be found in many lakes, rivers and streams across North America. I am among one of the largest fresh water fish and if you catch me, I will put up a good fight.