Differences in juvenile trophic niche for two coastal fish species that use marine and estuarine nursery habitats

Abstract

In coastal regions, age-0 juveniles of many fish species are capable of recruiting to either marine or estuarine nursery habitats, yet the ecological consequences for cohorts that use marine versus estuarine nurseries is poorly understood. In the present study, stable isotope (δ 13 C, δ 15 N) and stomach contents data were used to compare trophic ecology associated with differential habitat use for age-0 bluefish Pomatomus saltatrix and bay anchovy Anchoa mitchilli from 2 habitats: Maryland's (USA) inner continental shelf (shelf) and lower Chesapeake Bay (estuary). Bluefish occupied equivalent trophic positions (approx. 4.0 to 4.2; δ 15 N-and diet-based estimates) as tertiary consumers in the shelf and estuary. In contrast, bay anchovy were secondary-tertiary consumers with trophic position estimates of 3.5 to 3.8 in the shelf and 3.5 in the estuary. A C:N ratio proxy for lipid content was higher in the shelf cohorts for both species, and weight-at-length was also higher for shelf bay anchovy than estuarine bay anchovy. Estuarine cohorts of both species occupied a larger isotopic niche (i.e. convex hull area), yet 2-source mixing model results indicated that estuarine cohorts derived > 80% of their biomass from pelagic food webs alone. Conversely, shelf cohorts more equitably integrated pelagic (bluefish: 45 ± 7% [SD], bay anchovy: 46 ± 12%) and benthic food webs. The present study indicates that the juvenile trophic niche of these species can vary significantly across habitats and provides initial evidence that cohorts recruiting to Maryland's shelf can realize more diverse (i.e. utilization of multiple food webs) or superior (i.e. increased condition -bay anchovy only) foraging conditions than cohorts recruiting to proximal estuaries.

Fish Species Distribution in Seagrass Habitats of Chesapeake Bay are Structured by Abiotic and Biotic Factors

“…The effects this decline may have had on associated fish fauna, particularly those of commercial or recreational importance, remain poorly documented. Most studies of Chesapeake Bay habitats have focused on single species (Dorval et al 2005b(Dorval et al , 2007Grubbs and Musick 2007), on a few species (Woodland and Secor 2011), or on lower trophic levels (Kimmel et al 2006). Although there are valuable studies of commercially important juvenile fish-habitat relationships in Chesapeake Bay, e.g.…”

The range of juvenile movements of estuarine and coastal nursery dependent flatfishes: estimation from a meta-analytical approach

“…Indeed, environmental gradients induce patterns in many of the natural tracers (carbon stable isotopes δ 13 C; Le ; otolith geochemistry (Sr/Ca ratio); de Pontual et al, 2003;Gillanders, 2005) that are used to identify segregation. Fish otolith microchemistry (Brown, 2006; Fodrie and Herzka, 2013) and stable isotopes (Kostecki et al, 2010;Woodland and Secor, 2011;Morat et al, 2014) are reliable methods for tracing upstream-downstream gradients and for distinguishing between the use of estuarine and coastal habitat. Along the coastline, otolith geochemistry can also discriminate nursery areas at the mesoscale (Dierking et al, 2012;Tanner et al, 2012); but the lack of small-scale patterns in habitat signature prevents geochemical tracers, and also stable isotopes, from discriminating finer-scale segregation (Hanson et al, 2004).…”

Diet shifts in a native mesopredator across a range of invasive lionfish biomass

“…Measurements of muscle C:N ratios can also serve as a proxy for lipid content ), and were calculated as a component of SIA. Samples with larger C:N ratios are higher in fat content, as lipids are richer in carbon than the amino acids predominant in lean muscle (Woodland & Secor 2011). Graysby stomach fullness was assessed to link physiological condition indices to the ecological process of foraging, and was measured using a metric described by Haram & Jones (1971).…”