Sunday, September 21, 2008

Marikina River and the "janitor" fish

My newest environmental science research project is to determine the evolutionary biology of invasion by the "janitor fish" in Marikina River. Today we made our first survey and collections. Marikina River is the"greenest"in Metro Manila but that is just on the surface.










One master's student is doing her thesis on biotic integrity and a volunteer MD is working on the project too.





The "janitor fish (Pterygoplichthys sp) is the dominant fish now in the river,displacing traditional Marikina food fishes such as dalag and hito.




The fish are collected and left to rot on the riverbanks.





Despite this, there is still some subsistence fishing on the river.




The highest densities of the fish are observed near sewage outfalls where they find food to eat.

It is likely that the fish can be controlled if we can clean up the river!

BTW the name "janitor fish" insults janitors. The fish thrive in dirty rivers and don't clean them up. Janitors on the other hand, clean up your schools and offices and hate dirty environments.

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