September 21, 2006
Fort Ross, California Abalone and Urchin Survey
by Greg Holzer
Sea Urchin and Abalone transect
surveys in northern California
Photo Credit: Shannon Fitzgerald.
The California Department of Fish and Game (DFG), leads red abalone and red sea urchin density surveys each year at designated sites in northern California. The survey teams include divers from the department, Bodega Marine Laboratory (BML), Humboldt State, and volunteer AAUS-certified scientific divers. In 2006, the dive surveys were lead by Dr. Laura Rogers-Bennett and were conducted at three sites: Timber Cove, Fort Ross, and Van Damme State Park. At two of the sites, density and size frequency data were collected at multiple depths, while at Van Damme the sixth year of recruitment monitoring was completed, along with the start of a large-scale red abalone tagging program. As one of the two volunteer AAUS-certified scientific divers, I was very pleased to be able to join in on the Fort Ross surveys scheduled for September 11-15, 2006. The dive teams are supported by the department’s Wildlife protection patrol boats, Captains, and mates. Funding for many of these surveys is made possible by the recreational abalone fishing stamp funds and the Recreational Abalone Advisory Committee.
Survey sites range along the Sonoma and Mendocino County coastlines. Protocols involve pairs of divers laying a 30-meter transect tape on a specific heading, then swimming along the transect while completing a datasheet, and tabulating measurements and quantities of selected species that occur within one meter on each side of the tape. The starting point of each transect is identified with its GPS coordinates. Surveyed species include red, flat, and pinto abalone as well as red and purple sea urchins. In addition, selected algal species and certain associated species (e.g., bat stars), as well as notes on seafloor composition are recorded. Typically, it takes between 30 and 60 minutes to complete a transect, depending on the number of animals and general sea conditions, which can occasionally get interesting in some of the shallower spots, with kelp and an energetic surge.
The divers had as their base of operations the DFG’s enforcement vessel P/B Marlin, a 54-foot aluminum catamaran, skippered by Captain Keith Long, with Warden Ed Morton as crew. The Marlin is equipped with a 17-foot Rigid Hull Inflatable and electric/hydraulic hoist for launching it. In addition, BML supplied a 14-ft. Zodiac with a 25-horse motor. The Marlin is a very capable diving platform, and with this equipment combination, we were able to field four teams of divers to lay and survey twelve, 30-meter transects each of the three days. U.C. Santa Cruz provided a portable compressor so that empty tanks could be filled during diving operations, minimizing the number of tanks that had to be handled, and preventing the need to load and unload tanks during the cruise.
The cruise plan was to depart Spud Point Marina in Bodega Bay about 0800 each day, anchor near the site, and launch divers in the Zodiacs with tanks for two morning dives. We would return to the Marlin for lunch, a bit of rest, and then finish with one afternoon dive. The Marlin returned to the marina each evening. Lunches were provided (and prepared) by the DFG crew (hamburgers and grilled chicken, with the usual “accessories”), and there was a good stock of snacks and drinks, as well.
The results from the Fort Ross survey along 37 transects showed that we encountered 1,252 red abalone, 2 flat abalone (pebbly mantle) and 3 pinto abalone (bright yellow tentacles in the respiratory pores). In addition, we saw 947 red sea urchins and 2 purple sea urchins, not to mention the zillions of bat and ochre stars. Interestingly, the flat abalone were at the shallower transects while the pintos were in deeper water and on the very tops of boulders, which is typical for this species. Not many divers know that we have three species of abalone on the north coast, not to mention the occasional black abalone in the shallow and intertidal habitats. Water temperatures for this cruise were in the low to mid 50F range, and visibility varied from about five feet in turbulent areas, to near 25 feet on some deeper transects.
It’s worth noting that this cruise was originally scheduled for five days, September 11-15. As is typical of this area, though, wind and seas picked up after a few days, safe diving couldn’t be conducted, and Thursday and Friday had to be cancelled. However, due to the good weather Monday through Wednesday, and the number of divers available, we were able to complete the 36 scheduled transects (plus a spare one), and finish all work planned at the Ft. Ross site.
With that last paragraph as segue, I’ll add that there is a continuing need for divers for this work each year, from around mid August to late September. If you’re interested in this sort of research, and are AAUS-certified, DFG would like to hear from you. You can email Dr. Laura Rogers-Bennett.
Posted by Dida at September 21, 2006 3:27 PM
