Can otolith chemistry be used for identifying essential seagrass habitats for juvenile spotted seatrout, Cynoscion nebulosus, in Chesapeake Bay?

Abstract

We investigated the variability of otolith chemistry in juvenile spotted seatrout from Chesapeake Bay seagrass habitats in 1998 and 2001, to assess whether otolith elemental and isotopic composition could be used to identify the most essential seagrass habitats for those juvenile fish. Otolith chemistry (Ca, Mn, Sr, Ba, and La; δ 13 C, δ 18 O) of juvenile fish collected in the five major seagrass habitats (Potomac, Rappahannock, York, Island, and Pocomoke Sound) showed significant variability within and between years. Although the ability of trace elements to allocate individual fish may vary between years, in combination with stable isotopes, they achieve high classification accuracy averaging 80-82% in the Pocomoke Sound and the Island, and 95-100% in the York and the Potomac habitats. The trace elements (Mn, Ba, and La) provided the best discrimination in 2001, a year of lower freshwater discharge than 1998. This is the first application of a rare earth element measured in otoliths (La) to discriminate habitats, and identify seagrass habitats for juvenile spotted seatrout at spatial scales of 15 km. Such fine spatial scale discrimination of habitats has not been previously achieved in estuaries and will distinguish fish born in individual seagrass beds in the Bay.Extra keywords: estuarine-dependent fish, natural tag, otolith microchemistry, seagrass bed discrimination.

Chemical signatures in the otoliths of a coastal marine fish, Menidia menidia, from the northeastern United States: spatial and temporal differences

“…Sites within locations were located within approximately 5 to 10 km of each other. Such small-scale differences have also been identified in other studies (Thorrold et al 1998a,b, Hamer et al 2003, Dorval et al 2005. It is possible that these small-scale differences observed in Menidia menidia otoliths reflect small-scale differences in water chemistry among sites.…”

“…Differences in elemental signatures have been identified in fish from different estuaries (Thorrold et al 1998b, Gillanders 2002b, rivers (Walther et al 2008), reef habitats (Patterson et al 2004), seagrass beds (Dorval et al 2005), coastal areas (Campana et al 1999, Warner et al 2005, and oceanic regions (Ashford et al 2005), thus supporting the idea that otoliths can be used as natural tags. The spatial scales at which habitats can be discriminated, however, is still being investigated and will likely differ among systems (see review Gillanders 2002b).…”

“…While most work examining the usefulness of otolith geochemistry as a natural tag has focused on isolated habitats, such as rivers or estuaries, and large spatial scales, recent studies have been conducted that show promise at smaller spatial scales. Among estuaries, it is possible to discriminate habitats at spatial scales on the order of 100s of kilometers apart (Thorrold et al 1998b, Gillanders 2002b, Patterson et al 2004, and, more recently, on very fine spatial scales of approximately 15 km within estuaries (Dorval et al 2005). Evidence of such discriminatory power in coastal or marine environments of fish not dependent on estuaries is still sparse.…”

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“…in recent years biologists have explored stable isotope relationships to these variables and have found, for instance, that δ 15 N and δ 87 sr are enriched in fish moving from estuarine to deep water habitats, and δ 13 C is enriched in seagrass habitats (Hobson, 1999: 320-321;Nagelkerken and van der Velde, 2004 Hanson, Koenig, and Zdanowicz, 2004;Dorval et al, 2004;Kennedy et al, 2005;Martin and Thorrold, 2005;Surge and Walker, 2005;Comyns et al, 2008;Fodrie and Herzka, 2008;Fodrie et al, 2010;cf. Chittaro et al, 2005cf.…”

Otolith research and application: current directions in innovation and implementation

“…Representative case studies of Daverat et al (2005), Tzeng et al (2005), McCulloch et al (2005), Dorval et al (2005) and Hobbs et al (2005) demonstrated the utility of otolith chemistry in tracking movements and/or habitat shifts throughout the life history of fish, which, in turn, can be used to infer stock structure and population connectivity (Fowler et al 2005;Stransky et al 2005). Similarly, Gillanders and Joyce (2005) used otolith chemistry to differentiate aquaculture and wild-harvest yellowtail kingfish (Seriola lalandi), whereas Niva et al (2005) examined the effectiveness of alizarin-red-stained otoliths as a cost-effective mass-marking tool.…”