## Tuesday, April 2, 2013

### Hitch-Hiking Fish: A Biological Rarity

For the first time, live vertebrates have been found to have made it all the way from Japan from the United States. When a blue fiberglass boat (one of many that have washed up) appeared on the shores of Long Beach, Washington, crews headed out to investigate biological risk and plan removal. But what they found surprised them. Hitching aboard the boat's hold were five live fish, native to Japan. The fish had apparently made their way into the boat, and floated across in the sea water within the
vessel.

 One of the five fish that floated across the Pacific in a small boat. [Photo: Washington Dept. of F&W]

The fish, Oplegnathus fasciatus- also known as striped beakfish, striped beakperch, barred knifejaw, or rock bream are native to Asian waters in Korea, Japan and China.  The fish probably entered the back compartment of the vessel where they were found, then became stuck as the boat drifted across the Pacific.

 Range of O. fasciatus.  Note that there are no points between Japan/Asia and Washington, as the boat likely floated across the Northern Pacific. [Map: aquamaps.org]

The sheer probability of this is slightly amazing- in order for this to happen, the fish must have first been trapped inside the vessel, and survive months of stressful through storms, temperature variations, and jostling.  Unlike intertidal invertebrates, which are used to a stressful and changing environment, fish are much more delicate and likely to die from stress or abrupt changes in water characteristics.  The reason for this is a temperature-sensitivity factor called 'Q10' or temperature coefficient.

Q10 is the rate at which your metabolic rate increases with an increase in ambient temperature.  More specifically, for every temperature increase of 10 degrees celcius, your metabolic rate is multiplied.  Fish have a notoriously low Q10, meaning that a slight change in water temperature can actually double their metabolic rate.  A Q10 of '2' means that for every 10 degrees celcius, an animal's metabolic reaction rates double. A Q10 of '3' means that it would triple, and so on.
The equation for Q10, or the temperature coefficient.
Here, R = rate of biochemical (enzyme) reactions within the body, both original (R1) and with the new temperature (R2)
and T = body temperature (generally in Celcius), both original (T1) and in new temperature (T2).

Most animals fall within a Q10 range of 2 or 3.  Also, keep in mind that most critters (such as you and me) can use 'homeostasis' or maintaining a particular body temperature to prevent abrupt changes.  Enzymatic activity in animals (the chemical reactions that keep your body going day to day) is very sensitive to temperature, and therefore it is essential that we keep our body temperatures in a relatively stable range from which it rarely changes- say 98.6.  That is why a fever of 102 degrees might be so dangerous for us.  Each species has a slightly different 'peak' temperature where their bodies operate best at.  We can slightly increase or decrease our metabolic rate (exercising, or sitting on the couch), but to a very minor degree without serious consequences.

 Q10 reaction rate chart.  Read more at: http://www.calpoly.edu/~bio/EPL/pdfs/SampleLectureBIO162.pdf

Fish have a wide range of Q10 values, but as a result of being poikilothermic (having changing body temperature) unlike mammals, they are much more sensitive to temperature changes.  Think of how sad your goldfish looks if you change his water and make it a little too cold, or a little too warm- his metabolic rate is going crazy.

It is a wonder that these guys survived their entire voyage.  Unfortunately, of the five fish, only one is still alive- the others dying in transport and removal (likely from heat and handling stress once the boat washed up), showing how delicate they really are.  If the lone survivor continues to thrive, it will be placed on display at the Long Beach Aquarium.  I'm rooting for him.

If you'd like to learn more about temperature regulation in animals, there is an excellent introductory lecture at: http://www.calpoly.edu/~bio/EPL/pdfs/SampleLectureBIO162.pdf.
Enjoy!