Southern Oregon Surfperch Studies, 1991-2000, Final Report
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FINAL REPORT SOUTHERN OREGON SURFPERCH STUDIES Prepared by Darrell Pruden Marine Resources Program Oregon Department of Fish & Wildlife December 2000 This project was financed in part with funds provided by the Federal Aid in Sport Fish Restoration Program through the U.S. Fish and Wildlife Service. SOUTHERN OREGON SURFPERCH STUDIES 1991-2000 FINAL REPORT INTRODUCTION Several members of the surfperch family (Embiotocidae) are an important part of the Oregon shore and estuary recreational fishery. There has also been a recent increase in the commercial take of redtail surfperch on the southern Oregon coast for markets in California. The surfperch season in Oregon is open year-round for recreational anglers, but closed for commercial fishing in August and September. The overall condition of the surfperch population along the Oregon coast had been assumed to be healthy, but because of the low fecundity of these live-bearing fishes, increased effort by both sport and commercial fishers could pose a threat. In 1990, the Oregon Department of Fish and Wildlife (ODFW) intensified research on the most often angled species of surfperch in Oregon, to establish a biological database for use in future management. Fish were tagged for movement and harvest rate studies and carcasses were sampled for age structures, sex, maturity, and embryo information. The main focus was on redtail surfperch (Amphistichus rhodoterus) due to its accessibility and popularity, but the study also included striped surfperch/seaperch (Embiotoca lateralis), pile surfperch/seaperch (Damalichthys vaca), white surfperch/seaperch (Phanerdon furcatus), walleye surfperch (Hyperprosopon aregenteum), silver surfperch (Hyperprosopon ellipticum), and calico surfperch (Amphisticus koelzi). This report covers research conducted from December 1990 to December 2000. METHODS AND MATERIALS Study area Initially, a sampling program was set up to cover the south coast of Oregon from Florence to the California border with ODFW supervision coming from Charleston. Because the study area was too large to properly facilitate, it was later reduced to an area just north of the Umpqua River to the California border. The primary focus was on redtail surfperch so all accessible sandy beaches were included. The Coos Bay estuary was also sampled, with occasional samples taken from Winchester Bay (Umpqua River) and Bandon (Coquille River). 1 Carcass Collection Recreational angling volunteers were the primary source of fish samples (carcasses) and assistance in tagging. Signs describing the project, recruiting volunteers, and informing the angler who to contact were placed at common angler access points. Participating anglers were rewarded with baseball type caps with a designed surfperch logo to stimulate carcass collection and return of tags. An annual newsletter was distributed describing the project and emphasizing different themes each year, such as: fishing methods and tackle, migration, and species description. These newsletters were mailed out to volunteers and were distributed as handouts at various tackle shops. The large sample area made it necessary to set up systems to collect carcasses. In the Brookings area assistance came from a sporting goods store where carcasses were collected and stored frozen until they were transported to Charleston. In most of the remaining area a network of communication and collection was used. Anglers were asked to bring their carcasses directly to the Charleston office when possible. Volunteers were supplied with the following material: 18” x 36” 4 mil plastic bags, one gallon freezer bags, and preprinted “Rite in the Rain” cards to identify the catch. Information on the cards included: date, location, hours fished, number of anglers, and the name-address-phone number of the volunteer. The volunteers were then instructed on how to fill out the information and package the carcass. Each carcass was cataloged, fork length measured, sex identified, maturity noted, and ageing structures collected. In addition, snout to hypural plate length was measured from one “normal” embryo (Bennett and Wydoski, 1977) from each gravid female. The minimum length measured for the embryo was established at 10 mm. Initially, fecundity counts were conducted. These were soon eliminated because of observed ovary damage caused by angler filleting, and also after observing females aborting embryos during capture. Ageing Ageing was done in the winter months when carcass collection was slow. After two years of collection and observation, the decision was made to use only the pair of sagittae otoliths as the preferred ageing structure. Scale collection was discontinued because otoliths were easier to handle and consistently clearer to read. The otoliths were aged whole in an alcohol bath by using a dissecting microscope under magnification of 6 or 12 depending on the species, size, and clarity of the otolith. No other procedure was used to enhance the otolith in determining the age. Examination of the embryo otoliths provided a starting point from which to age the fish. This “birth check” was obvious in all species unless the otolith was crystallized. The international accepted birth date of January 1 was used (Chilton and Beamish 1982). Confirmation and validation of the age also came from recaptured tagged fish. 2 Tagging Migration and biological studies Tagging occurred annually starting in May 1992. Redtail, silver, striped, white, pile, and walleye surfperch were tagged. Volunteers were recruited to angle for surfperch at predetermined locations and to sacrifice their catch for tagging. Successful tagging required coordinating angler participation, cooperative weather, appropriate surf conditions and tides, and proper bait. Both ODFW staff and volunteers collected bait in advance to supply the volunteers on the chosen day. Ghost shrimp (Callianassa californiensis) were used to catch surfperch for estuary tagging, while ghost shrimp, sand worms (Nephtys californiensis), sand crabs (Emerita analoga), and sea mussels (Mytilus califonianus) were used for beach tagging. Tagging in the estuary was accomplished from a boat, with volunteers angling. Fish were deposited in a live-well and immediately released after tagging. Most estuary tagging was done at locations within the confines of Coos Bay. When tagging on the open coast the volunteers, which could be as many as 20 anglers, were asked to fish within a close proximity of the tagging station. After a fish was caught it was placed in a plastic ice chest measuring 12”x12”x25” (top removed) partially filled with fresh seawater (approximately 10 gallons). When six fish were in the cooler, or sooner if collection was slow, the fish were tagged with a yellow T-Bar anchor tag (see tag retention study mentioned later), fork length measured, and sex identified. The sex was identified externally by examining the modified ventral fin on males of one plus years. The tagged fish were then released by carrying them in a five-gallon plastic bucket partially filled with seawater back to the surf. It was important to keep fresh seawater in the cooler and release bucket, especially during clear warm weather. Tagging locations were from the mouth of Tahkenitch Creek south to the mouth of Pistol River (Figures 1 and 2). Except for a few tagging sites, successful historic fishing areas were chosen that were also easily accessible for volunteers. Areas such as the north spit of the Umpqua River, New River area, and the mouth of Elk River required either special vehicle transportation or landowner permission. These locations helped fill voids in the study area. Tag Retention Study Since very little tagging has been done on surfperch, a tag retention study was initiated under laboratory conditions on November 18, 1993 at the Oregon Institute of Marine Biology in Charleston. Fourteen redtail and one silver surfperch were captured and placed in a five-foot diameter fiberglass tank, which had an average capacity of approximately 300 hundred gallons of circulating seawater. One-half of the tank was covered in order to give the fish solitude. Due to varying water pressure in the water supply to the tank, an accurate measure of flow was not obtained. Air was pumped into the water with two plastic lines (1/4” ID) attached to aerating 3 stones. This not only added oxygen, but also gave the water turbulence to produce a more natural condition. Five days after capture all surfperch were tagged with yellow plastic T-Bar anchor tags (manufactured by Halprint pty.ltd in Australia). These tags were used because they offered excellent print durability (Waldman, J.R. 1989 and personal communication). The tag was inserted about midway and just below the dorsal fin near the start of the soft rays (Barss and Demory 1989). Care was taken to anchor the tag between the pterygiophores. The fish were monitored and fed daily for 48 days. They were then released at the same capture location (Bastendorff Beach near Charleston). Refer to Tag Retention Study on page 7 for results. RESULTS Carcass Collection Volunteers collected over 20,000 carcasses. More than two-thirds were redtail surfperch carcasses (Table 1). Most carcasses came from areas south of Cape Arago. An intensified inter- agency beach management strategy north of Cape Arago limited access, shifting redtail surfperch angling effort elsewhere. Redtail surfperch were found on every sandy beach sampled. Sample information and carcass handling by the volunteers was found to be very satisfactory. Carcass examination