Vic and I didn’t have space last week to report all the great news that we heard at the third annual Bolsa Chica Science Symposium. At this event, sponsored by the Amigos de Bolsa Chica, scientists presented the past year’s monitoring and research results from the restored full tidal basin at Bolsa Chica Ecological Reserve.
Mario Espinoza, a graduate student in the laboratory of Christopher Lowe at Cal State Long Beach, discussed use of the full tidal basin by sharks and rays. Espinoza monitored how temperature of the water affected distribution of various species.
Espinoza found eight species of sharks and rays, the most common being gray smooth hound sharks, leopard sharks, bat rays and shovel-nosed guitarfish. Round stingrays were common from May through September, but weren’t found in winter months. Rarer species were diamond, thornback and butterfly rays.
The shallows in the full tidal basin are warmer than deep water in the summer, and colder than deep water in winter. Espinoza found a higher abundance of sharks and rays in shallow water during the summer months. In the winter, they tended to hang out in deeper water, and there were far fewer of them. Espinoza also tallied 40 species of bony fish and 32 species of invertebrates, a large increase over early restoration numbers.
Thomas Farrugia, another graduate student in Lowe’s lab, monitored movement patterns of individual fish to determine their habitat preference.
After catching sharks and rays in seine nets, he tagged them with transmitters. A set of short receiving “towers” on the mudflats picked up the signals and tracked the movements of several animals simultaneously.
A novel feature of this research is that emitters give off high frequency sound waves rather than electronic signals. Sound carries better underwater than electronic signals. Monitoring the activities showed that shovel-nosed guitarfish are less active and have smaller ranges than gray smooth hound sharks.
One of Farrugia’s findings was that three out of nine gray smooth hound sharks tagged in 2008 returned this summer. Among the guitarfish, two out of 10 returned in 2009.
Although the numbers weren’t statistically significant, the returnees were all large females. Farrugia speculated that the females may have returned to the full tidal basin to give birth. One important value of coastal wetlands is that they serve as nurseries for many ocean fish species.
These sharks and rays range from Seal Beach to Newport Beach, and are surprisingly abundant. Farrugia estimated that on any given summer day, Bolsa Chica will have several thousand sharks and rays in the full tidal basin. Seal Beach has the highest abundance of round stingrays in the world. Round stingrays have certainly been visible from the walkbridge over Inner Bolsa Bay this summer.
All sizes of sharks, rays and other fish were found in these studies, showing that the full tidal basin is supporting a diverse population of juvenile and adult fish.
Jeannette Hendricks, a graduate student in Michael Horn’s lab at Cal State Fullerton, presented the results of her studies on elegant terns. Hendricks had the unglamorous task of collecting and identifying regurgitated and dropped prey, supplemented by observation of video recordings of fish being fed to chicks at nests.
Hendricks found that the terns utilized an amazing 52 species of fish as prey items over a two-year period. The bulk of the prey came from four species: kelp pipefish, anchovies, top smelt and grunion. She found that the percentage of pipefish in the diet has been going up over a 10-year period, and now makes up 60% of the birds’ diet.
Tyler Filsik, another graduate student in Horn’s lab, reported that the number of pipefish is also going up as a percentage of feed in sea birds of the North Sea.
Unfortunately, pipefish have a lower energy content compared to anchovies and sardines. Because pipefish are long and thin and writhe vigorously when caught, they also are more difficult for chicks to eat as well. Some long-term environmental change seems to be forcing terns to resort to less desirable food for their chicks.
Filsik fed elegant tern chicks in the lab on a diet that was 10% pipefish, compared to control chicks that were fed 100% anchovies. The chicks with 10% pipefish in their diet gained less weight, indicating that chicks in nature that are being fed a diet that is 60% pipefish are not doing as well as if they had more anchovies and sardines in their diet.
Sadly, Horn also reported a total breeding failure of the world’s largest breeding colony of elegant terns at Isla Rasa in the Sea of Cortez.
El Niño conditions there resulted in not enough prey, and the colony of 200,000 nesting pairs produced no chicks. There are only five colonies of elegant terns in the world, with Bolsa Chica being the second largest. This year, Bolsa Chica is playing a critical role in the support of the entire species.
Kelly O’Reilly of the Department of Fish and Game closed out the meeting with some good news. She reported that there were a total of 317 nests of endangered California Least Terns at Bolsa Chica this summer, with 412 chicks and up to 363 fledglings.
A problem occurred early in the season when 37 nests were trampled by much larger black skimmers. Fish and Game biologists responded by placing metal cages over the nests to protect the chicks. This resulted in a loss of only 5% of the nests to predation. This was the best year out of the last four at Bolsa Chica for the struggling least terns.
Last week, we told you that a new world record may be set at Bolsa Chica this coming winter. Recently, Peter Knapp, a Fish and Game biologist, observed a black skimmer with a leg band that identified it as having hatched at Bolsa Chica in 1989, probably the first year that black skimmers nested there. That bird is now 20! If this bird can be refound in December, it will go on record as the longest living black skimmer ever observed in the wild.
Bolsa Chica is a remarkable place, and a remarkable story of how people persevered, saved it and restored it.
VIC LEIPZIG and LOU MURRAY are Huntington Beach residents and environmentalists. They can be reached at firstname.lastname@example.org .