By Tom Cervantes
Nature is full of great survival stories. One of these fascinating tales takes place in the seasonally intermittent streams throughout the Bay Area. The hero of this story is the California Roach (Lavinia symmetricus). No, it is not the creepy-crawly pest that you find hanging near dumpsters, but rather a fish that only reaches the size of your pinky finger (5 inches maximum).
Its tiny body allows it to navigate through extremely shallow streams and to inhabit small ponds. These ponds evaporate as summer temperatures rise, leaving warm, salty water behind. The fish is able to withstand water temperatures reaching upwards of 95 degrees F. There are even reports of it being able to survive streams that are damaged by sewage runoff. Typically, such harsh conditions prevent aquatic life from sustaining healthy population size; however, the hardy California roach has amazingly adapted to tolerate the most inhospitable water conditions. This adaptation allows the little fish to survive during the dry summer months, until the winter and spring rains return, replenishing our neighborhood watersheds.
It is likely that you have encountered schools of roaches in our local ponds and streams, as they are fairly common. The fish’s five-inch, or smaller, body is skinny with a bluish or grey top and a silver-metallic color on its underside. It can also have a black line running laterally along both sides of its body. During breeding periods, orange or red markings may appear under the chin and at the fins. It has large, round eyes that cover much of its round head.
The California roach has a voracious appetite and feeds mainly on algae sources along the stream bottoms, though they are not opposed to the occasional small insect lunch or even a crustacean from time to time. When bugs are plentiful, the roach may switch to an insect-only diet, providing a natural service for me and you. Sometimes this fish serves as the meal for larger predatory fish. Its role as a both predator and prey means that the California roach in integral to our local watershed’s food chain and long-term health.
A small fish like the California roach must produce a lot of young to increase the odds of species survival until the next rainy season. Breeding occurs during the end of the wet months, from March through June. The females will deposit up to 2,000 eggs along gravel substrate. Competing male fish will follow closely behind her, fertilizing her deposited eggs. Once this ritual has taken place, the parents are free to go. The gravel provides the protection for the eggs during their 2 to 3 day incubation period. Once hatched, the young will hide amongst the gravel until they are large enough for more open waters. As a result of such aggressive breeding techniques, the populations of this fish can outnumber other fish species in a system 100 to 1.
The ability for such a small fish to thrive against such difficult conditions and predation is an awe-inspiring tale of survival of the fittest. Sometimes the fittest are the tiny, overlooked creatures like our California roach.
Photo credits (top to bottom): Rene Reyes; San Francisquito Watershed Council; Carl Page, ARS Consulting.