Sunday, September 7, 2008

Fish monitoring on the Ventura River

I recently heard "When modern people think of the San Buenaventura River, they think of a mostly dry river that runs just to the west of the town of Ventura and empties into the ocean above the Ventura County Fairground and Surfer's Point." Even Kevin Costener, who grew up in Ventura, stated in a recent interview that "The river used to have salmon in it... and most people wouldn't even know it now... "

Until recently, nobody was really even looking for fish in the river. But as planning continues for the removal of Matilija Dam (now slated for 2014,) "baseline" information will become very important to demonstrate the response of the ecosystem to one of the largest dam removal projects ever considered.

Recognizing this, in 2006 and 2007 the CA Department of Fish and Game sponsored a fish survey conducted by consulting biologists Thomas Paine and Associates. (Two large adult steelhead were documented in the lower Ventura River last year.) This year, the Matilija Coalition applied for grants from DFG and Patagonia to augment funding from the previous years to ensure continued data collection in 2008.

Very little is actually known about the response of the endangered southern steelhead to the extreme variations in the southern California rivers from year to year. Characterized by the unpredictable 'boom and bust' cycles of flood and drought, our rivers seem inhospitable to this sensitive indicator species. Research into the annual variations and population densities is a timely topic, with dam removal and climate change right around the corner. And as our Stream Team data has demonstrated, the value of long term monitoring far outweighs just visiting the river once or twice.

Last week we went out to observe the biologists working in the field. Snorkel surveys are conducted by a group of trained biologists, who systematically swim upstream and count the number of trout in selected pools. The counts include age classification, separating this year's smolt from the yearlings and adults. In this single pool, the count averaged between 180 and 190 fish! Highlighting the dramatic annual variability, the same pool only held a handful of trout during last year's survey. Although these are not adult steelhead, some of these native rainbow trout may become anadromous and enter the ocean.

See if you can spot the trout in this video. Most of the smaller fish are chub and stickleback. It's great to see that despite all the stresses on the system, the river continues to support a substantial population of native fish.

(video courtesy of Brett Millar)