June 27, 2016

Huge influx of Pelagic Red Crabs in San Diego waters


An old friend paid us a visit this past month in San Diego.

The pelagic red crab, also known as the tuna crab, has piled up on our shores in record number.
This conspicuous invertebrate is a species of squat lobster that tends to aggregate off the continental shelf of Mexico. It's scientific name is Pleuroncodes planipes.

Every couple of years, the tuna crab will follow a warm water current up to San Diego. This is sort of a natural rhythm. The warm waters generally coincide with the El Nino year. During these warm water years, the animals tend to swarm together in an attempt to mate. For some reason. that nobody seems to understand - the red tuna crab ends up getting washed on shore during these swarming events.

Last year, we had a huge wash up in Mission Bay and Ocean Beach. But this year, the pile up of these crabs was even more extreme. Here is a picture of a pile of red pelagic crabs near the gate to my marina in Mission Bay. I took this photo mid-June 2016.


an enormous pile of red tuna crabs near my boat in Mission Bay

Now, it is important to remember that 2016 is not a El Nino year. So, biologist believe that the washing up of crabs in southern California may be more of a climate change event.

That is - now that we are seeing persistently warmer waters in our Pacific Ocean, the swarming of this invert in our waters may be the new normal.

There are bound to be reverberations in the ecosystem. The crab is an important food item for marine birds and fish (such as tuna, yellowtail, amberjack and sharks).

As long as the northward currents remain warmer than usual, we better get used to our new red friends.

1 comment:

Kevin Curran said...

Oddly, I don't see a single one today - and the waters are warmer - back into the mid-60's.

Perhaps they have gone farther north.