Fisheries Management and Ecology
Fisheries Management and Ecology, 2010, 17, 404–413
Habitat use patterns of newly settled spotted seatrout in estuaries of the north-western Gulf of Mexico
T. A. NEAHR Texas Parks and Wildlife Department, Coastal Fisheries Division, Corpus Christi, TX, USA
G. W. STUNZ Department of Life Sciences, Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, Corpus Christi, TX, USA
T. J. MINELLO Fisheries Ecology Branch, NOAA Fisheries Service, Southeast Fisheries Science Center, Galveston, TX, USA
Abstract This study examined habitat use patterns of newly settled spotted seatrout Cynoscion nebulosus (Cuvier) across several Gulf of Mexico estuaries. Intensive sampling using an epibenthic sled was conducted in three Texas bays and among three potential habitat types. A long-term data set (1982 to 1997) from the National Marine Fisheries Service was also used to examine C. nebulosus habitat use patterns in both marsh and seagrass- dominated bay systems for broad regional comparisons along the north-western Gulf of Mexico. Vegetated habitat types such as seagrass and marsh supported the highest densities and use was dependent upon availability of particular vegetated habitat types. In laboratory mesocosm experiments, both wild-caught and hatchery-reared C. nebulosus, showed strong selection for structured and vegetated habitat types. These field and laboratory results suggest that seagrass meadows and marshes may be functioning as important habitat for C. nebulosus in Gulf of Mexico, and other habitat types such as oyster reef need further evaluation.
KEYWORDS: hatchery-reared fish, mesocosm, salt marsh, sciaenid, seagrass.
can be complex. Specific distribution patterns may be Introduction caused by behavioural responses of fish to specific Estuaries are productive ecosystems that support habitat types. New recruits may increase their relative diverse communities, and numerous ecologically and fitness by selecting habitats that maximise growth rates economically important fish species use estuarine and minimise encounters with predators (Heck & habitats during critical phases of their life cycle Crowder 1991; Sogard 1992; Stunz et al. 2002). For (Weinstein 1979; Minello 1999). Primary functions of example, some fish selectively settle in seagrass (Bell & these areas include refuges from predation and pro- Westoby 1986), marshes (Minello 1999), coral reefs motion of rapid growth from abundant food supplies (Sale et al. 1994) and rocky reefs (Levin & Hay 1996), leading to subsequent recruitment to adult populations and these selection patterns can influence distributions (Heck & Thoman 1981; Kneib 1993; Beck et al. 2001). and abundance of fishes (Bell et al. 1987; Levin et al. Generally, estuarine fishes are not randomly distrib- 1997; Levin & Stunz 2005). The value of vegetated uted and the underlying mechanisms for this pattern habitat is well-documented, but few studies have
Correspondence: Gregory W. Stunz, Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412-5869, USA (e-mail: [email protected])
404 doi: 10.1111/j.1365-2400.2010.00733.x 2010 Blackwell Publishing Ltd. HABITAT USE PATTERNS OF SPOTTED SEATROUT 405 simultaneously focused on the relative value of sea- (Baltz et al. 1998; Rooker et al. 1998; Stunz et al. grass, salt marsh and non-vegetated bottom in terms of 2002), but it is unknown if other sciaenids exhibit habitat use (Rozas & Minello 1998; Minello 1999). similar behaviours. Despite these generalities concern- Given the decline of both salt marsh (Penland & ing C. nebulosus recruitment, few studies have exam- Ramsey 1990) and seagrass meadows (Short & Wyllie- ined specific habitat use preferences of juveniles when Echeverria 1996), a comparative evaluation of habitat given a choice of habitat types. types is needed for many species. Specifically, this study (1) examines habitat use Spotted seatrout, Cynoscion nebulosus (Cuvier), is patterns of newly settled C. nebulosus in three south one of the most sought after recreational fish in south- Texas bays, (2) assesses habitat use of C. nebulosus in east USA. In the Gulf of Mexico, 3.3 million anglers estuaries with limited seagrass habitat using long-term spent 23 million days fishing in 2003 and the most data sets from the northwestern Gulf of Mexico and commonly captured species was C. nebulosus (Van (3) examines C. nebulosus habitat selection preferences Voorhees & Pritchard 2004). While Texas has tradi- for both wild-caught and hatchery-reared fish using tionally supported an abundant C. nebulosus stock, experimental mesocosms. results from the Texas Parks and Wildlife DepartmentÕs (TPWD) long-term monitoring programme has raised Materials and methods some management concerns over decreasing availabil- ity of C. nebulosus in some regions (particularly South Habitat selection in south Texas bays Texas) that has resulted in stricter regulations (Green & Campbell 2005). Moreover, in an effort to supplement Cynoscion nebulosus were collected from Aransas Bay, natural recruitment of recreational fish stocks, the State Corpus Christi Bay and the Upper Laguna Madre of Texas has been carrying out a marine stock (Fig. 1). Aransas Bay is a bar-built estuary along the enhancement programme in Texas estuaries (Scharf Texas Gulf Coast lying between Corpus Christi and 2000). Currently, approximately 1 million C. nebulosus San Antonio bays. Halodule wrightii (Ashers) and fingerlings (about 40 mm total length) are released Thalassia testudinum (Banks) are dominant seagrasses annually into Texas estuaries. Recruitment and main- within the estuary. Spartina alterniflora (Loisel) forms tenance of sustainable populations rely on estuarine intertidal salt marsh habitat that lines the bayÕs nursery habitat availability and use, but there are perimeter. The northern reaches of Aransas Bay have considerable gaps in knowledge concerning specific extensive marsh complexes and aerial coverage of spatial patterns of habitat use for both wild-caught and marshes declines progressively southward. Corpus hatchery-reared C. nebulosus. Studies generating habi- Christi Bay is a bar-built estuary south of the Aransas tat use information have the potential to enhance the Estuary. Halodule wrightii is the dominant seagrass in success of management and enhancement programmes. the estuary. Spartina alterniflora intertidal salt marshes In Texas, C. nebulosus spawns from April to are common in many areas but are much less extensive October, with two peaks, one in June and another in than Aransas Bay. By contrast to Aransas and Corpus September (Rooker et al. 1998; Powell 2003). Spawn- Christi bays, the Laguna Madre is a bar-built hypers- ing sites are typically in deeper water and channels aline lagoon, extending from Corpus Christi Bay, adjacent to shallow flats and seagrass beds (Pearson Texas to Rio Soto la Marina, Mexico. The Laguna 1929). Newly settled juveniles are found in seagrass Madre is a negative estuary because of evaporation meadows, salt marshes and non-vegetated bottom losses exceeding freshwater inflows. The estuary con- (Baltz et al. 1993; Rooker et al. 1998), but there are tains four species of seagrasses: H. wrightii; T. testud- considerable differences in habitat availability in estu- inum; Ruppia maritima (L.); and Syringodium filiforme aries along the Gulf of Mexico. For example, in a (Kuetz). The Upper Laguna Madre differs from the south-western progression, estuarine habitats change other bay systems in this study as it is a seagrass- from marsh to seagrass-dominated systems, but the dominated system with very little intertidal emergent extent to which C. nebulosus adapt their habitat use marsh vegetation. All three estuaries support abundant patterns in response to changes in availability of populations of C. nebulosus but are characterised by certain habitat types is unknown. Previous habitat differences in vegetated habitat availability. selection studies have also predicted distributions of Juvenile C. nebulosus were sampled in seagrass, non- fishes based on experimental mesocosms (Fraser & Sise vegetated bottom and marsh edge (when available). 1980; Heck & Crowder 1991; Baltz et al. 1993). Seagrass habitats sampled were in meadows dominated Sciaenops ocellatus (Linnaeus), a sciaenid similar to by H. wrightii. Non-vegetated bottom habitat sampled C. nebulosus, selects specific vegetated habitat types was mud and sand bottom >1 m from the marsh edge