Compiled by Stillwater Sciences.
Tidewater Goby (image from CA Fish Website)
Federal Threatened (Central California Coast ESU, listed in 1997 [62 FR 43937])
Native Origin and Geographic Distribution
This species is endemic to California and is generally located along the California coast, mainly in small coastal lagoons and near stream mouths in the uppermost brackish portion of larger bays (SCREMP 1996). Historically this species ranged from the mouth of the Smith River, Del Norte County near the Oregon border to Agua Hedionda Lagoon in northern San Diego County (USFWS 2005). Tidewater goby localities include discrete lagoons, estuaries, or stream mouths separated by mostly marine conditions, and are generally absent from areas where the coastline is steep and streams do not form lagoons or estuaries (USFWS 2005).
Tidewater gobies have been observed in the Santa Clara River as far as three miles from the estuary/lagoon, between Ventura and Oxnard (SCREMP 1996), and also in the Santa Ynez River (USFWS 2005).
Estimating tidewater goby population trends is complicated because populations are controlled by environmental conditions (USFWS 2005). For example, when lagoons are breached due to flood events during the rainy seasons, populations of tidewater gobies generally decrease and then recover during the following summer (USFWS 2005). Current distribution still remains entirely within the original known range of the species, however, 23 (17 percent) of the 134 documented localities are considered extirpated and 55 to 70 (41 to 52 percent) of the localities are so small in size or have been degraded over time that long-term persistence is uncertain (USFWS 2005).
Life History and Timing
Although tidewater goby are short-lived (generally 1 year), they have relatively high fecundity (females produce 300–500 eggs/batch and spawn multiple times per year), with males defending eggs in burrows. Reproduction and spawning typically occurs during the spring and summer (April to June) in slack shallow waters of seasonally disconnected or tidally muted lagoons, estuaries, and sloughs. Males dig burrows vertically into sand, 100-200 mm [4 to 8 inches] and guard eggs (SCREMP 1996). Juveniles and adults can be found year-round, although they are most abundant in summer/fall.
Reproduction occurs at all times of the year, but generally male tidewater gobies begin digging breeding burrows in relatively unconsolidated, clean, coarse sand (averaging 0.5 mm [0.02 inch] in diameter), in April or May after lagoons close to the ocean (USFWS 2005). Individual burrows are at least 70 to 100 mm (3 to 4 inches) from each other (USFWS 2005). Female tidewater gobies aggressively spar with each other for access to males with burrows for laying their eggs (USFWS 2005). Female tidewater gobies can lay 300 to 500 eggs per clutch, depending on the size of the individual female tidewater goby, and can lay up 6 to 12 clutches per year (Swift et al. 1989, Swenson 1999). Male tidewater gobies remain in the burrow to guard the eggs that are attached to sand grains in the burrow ceiling and walls (USFWS 2005). Embryos require 9 to 11 days to hatch, during which the male tidewater goby cares for the embryos, rarely emerging from the burrow to feed (USFWS 2005). Tidewater gobies spawn regularly in water with salinities 8 to 15 parts per thousand (ppt) and temperatures 17 to 22 Celsius (°C) (62 to 71 degrees Fahrenheit) (USFWS 2005). Tidewater goby standard length at hatching is approximately 4 to 5 millimeters (0.17 to 0.25 inch), and are planktonic (unable to swim freely) for 1 to 3 days before they become benthic (USFWS 2005). The average size of tidewater gobies tends to be significantly larger in marshes (43 to 45 millimeters [1.7 to 1.8 inches] standard length) when compared to tidewater gobies from lagoons or creek habitats (USFWS 2005, Swenson 1999). This may be because the more stable physical conditions of the marsh foster improved growth or a more consistent or abundant supply of prey (USFWS 2005, Swift 1997).
The lagoons in which tidewater gobies are found range in size from a few square meters of surface area to about 800 hectares (2,000 acres). Most lagoons are much smaller, ranging from about 0.5 to 5 hectares (1.25 to 12.5 acres) (USFWS 2005). Tidewater gobies can use habitat in water that is comprised of 75 percent sea water (i.e., salinity of 28 parts per thousand), but generally are found in areas where water salinity is 12 parts per thousand or less (USFWS 2005). Tidewater gobies are usually collected in areas with water less than 1 meter (3.3 feet) deep (USFWS 2005). Tidewater gobies often migrate upstream into tributaries, as far as 1.0 kilometer (0.5 mile) from the estuary (SCREMP 1996). However, in the Santa Ynez River, Santa Barbara County, tidewater gobies are often collected 5 to 8 kilometers (3 to 5 miles) upstream of tidal lagoons areas, sometimes in sections of stream impounded by beavers (Castor canadensis) (SCREMP 1996, USFWS 2005).
Tidewater gobies are an estuarine/lagoon adapted species that may infrequently disperse via marine habitat but with no dependency on marine habitat for its life cycle (Swift et al. 1989, Lafferty et al. 1999a). They can tolerate large temperature and salinity ranges. Reproduction takes place in water between 9 to 25 °C (48 to 77 degrees Fahrenheit) and at salinities of 2 to 27 parts per thousand (USFWS 2005). Tidewater gobies generally inhabit areas with water temperatures 4–21.5°C (39.2–70.7°F) (USFWS 2005). Preferred salinities (ppt) for reproduction/spawning were identified as = 15 within a range of 2–27 ppt (Swenson 1999, USFWS 2005).
Tidewater gobies require stable lagoon or off-channel habitats, particularly during their relatively short larval stage (Lafferty et al. 1999a, Chamberlain 2006). Flood and breaching events can result in dispersal of tidewater gobies between estuarine/lagoon habitats, although survival is likely low and dispersal is limited. The distance between extirpated habitats and larger wetland source populations affects dispersal success and re-colonization potential (Lafferty et al. 1999a and 1999b). Gobies can persist in habitats that flood as long as a velocity refuge is present (Moyle 2002, Lafferty et al. 1999b).
The life stages that are likely most sensitive to changes in habitat conditions associated with flooding and breaching are eggs in burrows and pelagic larvae (Chamberlain 2006). Juveniles and adults can tolerate flooding/breaching in late fall/winter. Preferred substrates are sand, mud, gravel, and silt, particularly associated with submerged vegetation that is likely used for cover (USFWS 2005).
Tidewater gobies feed mainly on small animals, usually mysid shrimp, gamarid amphipods, and aquatic insects, particularly chironomid midge larvae (Swift et al. 1989; Swenson 1995; Moyle 2002). Swenson (1996) found that juvenile tidewater gobies are generally day feeders, although adults mainly feed at night (USFWS 2005). Tidewater gobies use three different foraging styles to capture benthic prey: plucking prey from the substrate surface, sifting sediment in their mouth, and mid-water capture (USFWS 2005). The variety of foraging methods allows tidewater gobies to utilize a wide variety of prey items in various habitats.
Native predators of tidewater gobies include small steelhead (Oncorhynchus mykiss), prickly sculpin (Cottus asper), and staghorn sculpin (Leptocottus armatus) (Swift et al. 1989, USFWS 2005). Predation by the tule perch (Hysterocarpus traski), and historically by the Sacramento perch (Archoplites interruptus), has probably prevented tidewater gobies from inhabiting the San Francisco Bay delta, an otherwise ideal habitat for tidewater gobies (Swift et al. 1989). Garter snakes (Thamnophis spp.) also probably prey on tidewater gobies. Rathbun (1991) suggested that robust populations of tidewater gobies, as well as threespine stickleback and prickly sculpins, would provide food for the twostriped garter snake (Thamnophis hammondii) in Santa Rosa Creek Lagoon.
Gobies are an important part of estuarine food webs, as they provide prey for larger fish and piscivorous birds (Swenson and McCray 1996). However, tidewater goby are highly susceptible to predation by introduced species, especially piscivorous fish and amphibians (Lafferty et al. 1999a, Lafferty and Page 1997). Sunfishes (Lepomis spp.) and basses (Micropterus spp.), have been introduced in or near coastal lagoons and estuaries and could prey heavily on tidewater gobies (USFWS 2005), as well as African clawed frogs in some freshwater habitats (Lafferty et al. 1999a, and Swift et al. 1997, Lafferty and Page 1997). In addition, the shimofuri goby, which has become established in the San Francisco Bay region (Moyle 2002), competes with and preys upon the smaller tidewater goby (Swenson and Matern 1995). Introduced yellowfin goby and shimofuri goby may also compete with or prey on tidewater goby (Swenson and McCray 1996 and Swenson 1999, as cited in Moyle 2002). At least four species of Asian estuarine and freshwater gobies and the rainwater killifish (Lucania parva), have been introduced to California and may compete or displace tidewater goby when they occur in the same areas.
Many piscivorous birds, including egrets (Egretta spp.), herons (Ardea herodias, Butorides striatus, Nycticorax nycticorax), cormorants (Phalacrocorax spp.), terns (Sterna spp.), mergansers (Mergus spp.), grebes (Podiceps ssp., Podilymbus spp., Aechmophorus spp.), and loons (Gavia spp.), frequent the coastal lagoon habitats, mainly in fall and winter, and may feed on tidewater gobies (Rathbun 1991). Tidewater goby appear to prefer shallow depths ( 20 cm (8 in) (Gawlik 2002). However, reported depth preferences may be biased because sampling equipment commonly used to survey tidewater gobies, such as beach seines, are limited in their utility to sample deeper habitats.
Sensitivity to Anthropogenic Watershed Disturbances
The main threats to tidewater goby include changes in water quality, degradation and loss of habitat due to urbanization, and predation from invasive species such as the African clawed frog. It is estimated that tidewater goby has disappeared from 74 percent of the coastal lagoons south of Morro Bay.
Gobies are sensitive to impacts such as lack of freshwater due to diversions, pollution, siltation, and invasion of non-native species, such as the western mosquitofish (Gambusia affinis), which is a competitor, and the African clawed frog (Xenopus laevis), which is a predator (USFWS 2005, Lafferty et. al 1999a).
According to the U.S. Fish and Wildlife Service, which has prepared a final recovery plan for the tidewater goby, the key threats to the goby that are relevant to the Santa Clara River watershed include agricultural discharges, sewage treatment effluent, water diversions, and exotic species (USFWS 2005).
- How do tidewater gobies re-colonize areas in Santa Clara, particularly after high flows due to storm events?
- Is it possible to improve connectivity of lagoon habitat?
- Are non-native fish (sunfish, bass) having a greater impact than non-native amphibians (African clawed frog, bullfrog) on tidewater gobies? If so, why?
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