Site Fidelity of Mummichogs (Fundulus heteroclitus) in an Atlantic Canadian Estuary

Decimal coded wire tags were used to measure individual growth rates of mummichogs (Pisces: Fundulidae) within tidal marshes on Sapelo Island, Georgia, USA. Mummichogs (n = 17 508) were marked and released at 3 sites with different levels of complexity in their tidal channel drainage networks. The proportion of recaptures (average 19%), which varied from 6.4 to 43.3% among sites and release dates, was inversely related to relative complexity of the tidal drainage networks. Gender-specific differences were detected in size metrics and growth rates. Mean (± SD) growth rates (mm d -1 total length, TL) of individuals at large for 28 to 56 d prior to recapture ranged from 0.062 ± 0.044 to 0.274 ± 0.060 for males and 0.071 ± 0.036 to 0.279 ± 0.062 for females, with the least and most rapid growth rates associated with complex and simple tidal drainage networks, respectively. A 'common garden' experiment was conducted to test the hypothesis that there were genotypic differences in growth potential seemingly associated with landscape structure. Two size classes (40-50 and 55-65 mm TL) of individually marked mummichogs from drainage networks characterized as simple (high growth) and complex (low growth) were raised in the laboratory for 42 d on each of 2 daily rations (10 and 30% wet body mass) of minced fresh-frozen grass shrimp. There was no significant difference in mean (± SD) daily growth rates of mummichogs from the 2 sites (simple: 0.283 ± 0.124 and complex: 0.299 ± 0.131) when reared under the same conditions. Although there was no evidence of a genotypic difference in growth potential between these local populations of mummichogs, a possible association between landscape structure and gene expression reflected in the spatial variation of fish growth within tidal marsh ecosystems remains to be explored. KEY WORDS: Coded wire tags · Estuary · Genome · Fundulus heteroclitus · Killifish · Mummichog · WetlandsResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 386: 207-219, 2009 with spawning areas, as a likely mechanism producing genetic and phenotypic population sub-structuring from limited gene flow among locations even in the absence of effective physical barriers to movement.The research reported in this paper begins to explore the issue of whether spatial variation at a landscape scale is reflected in biotic variation at the molecular level (i.e. genetic variation or variation in gene expression) within estuarine organisms. In this study, spatial variation in the complexity of tidal marsh channel networks was used as a metric of estuarine landscape structure, and individual growth rates within populations of the mummichog Fundulus heteroclitus was a metric of phenotypic variation that could reflect spatial variation in the genome.Populations of Fundulus heteroclitus are resident year-round in marshes along most of the Atlantic coast of North America, where 2 sub-species seem to divide the range (F. h. macrolepidotus northward of Chesapeake Bay, and F. h....

Section: Field Recapture Ratessupporting

confidence: 68%

Section: Abstract: Coded Wire Tags · Estuary · Genome · Fundulus Hetmentioning

confidence: 99%

Genotypic variation does not explain differences in growth of mummichogs Fundulus heteroclitus from simple and complex tidal marsh landscapes

Kneib¹

2009

“…Direct estimates of adult dispersal distance are not known for F. grandis. Mark-recapture dispersal estimates for the closely related F. heteroclitus, which inhabits salt marshes along the Atlantic coast of North America, ranged from 200 m to 3.6 km within a single year (Sweeney et al 1998, Skinner et al 2005. If the genetic structure of F. grandis is predominantly shaped by current-day dispersal and distributional patterns, we would expect to find a pattern of IBD across the Gulf with significant genetic differentiation among populations due to low levels of dispersal.…”

Section: Introductionmentioning

confidence: 99%

Contemporary and historical influences on the genetic structure of the estuarine-dependent Gulf killifish Fundulus grandis

Williams¹,

Brown²,

Crawford³

2008

In comparison to species living in open marine environments, estuarine-dependent species are expected to exhibit stronger genetic population structure due to dispersal limitations. Estuarine habitats are relatively transitory on geological time scales; thus, populations may not be at migration-drift equilibrium, which could confound estimates of current day gene flow or selection. We used 8 nuclear microsatellite loci to investigate the genetic structure of the estuarine Gulf killifish Fundulus grandis across 10 populations along the northwestern and northeastern Gulf of Mexico. Patterns of isolation by distance, spatial autocorrelation, and assignment tests indicate that dispersal is limited and occurs primarily between neighboring sites. Principal component analysis and Bayesian clustering revealed evidence for genetic discontinuities located in Mobile Bay and western Florida which are near hypothesized biogeographical boundaries. There was also a significant negative relationship between genetic diversity and latitude, a pattern consistent with the presence of hypothesized refugia in the southern Gulf regions during the Pleistocene that later recolonized the northern Gulf. Results suggest that populations may be at or near migration-drift equilibrium at a regional scale (e.g the western Gulf), but that dispersal barriers and potential historical signatures on population structure will need to be taken into consideration at larger spatial scales.

“…However, the other restoration site, Bull Island, is separated from these 2 sites by the leveed main channel of the Napa River, making it less likely that there is an exchange of free-swimming juvenile fish between this and other marshes. Numer-250 Cohen & Bollens: Diet and growth of Mississippi silversides and yellowfin gobies ous estuarine and salt marsh studies have shown that both juveniles and adults of several wetland species display strong site fidelity to local intertidal marsh creeks (Potthoff & Allen 2003, Teo & Able 2003, Skinner et al 2005. Concurrent investigation of the wetland food web at our study sites using stable isotopes also suggests that both yellowfin gobies and Mississippi silversides display some measure of site fidelity and that fish diet bases at Bull Island were significantly different than those at Coon Island and Pond 2A (Howe & Simenstad 2005).…”

mentioning

confidence: 99%

Diet and growth of non-native Mississippi silversides and yellowfin gobies in restored and natural wetlands in the San Francisco Estuary

Cohen¹,

Bollens²

2008

We examined how wetland restoration status influenced habitat quality for fishes by comparing otolith-calculated growth rates and diets of 2 abundant non-native fish species, the locally transient planktivorous Mississippi silverside Menidia audens and the resident demersal-feeding yellowfin goby Acanthogobius flavimanus, in 2 wetlands undergoing restoration ('restoring' wetlands) and 1 natural wetland (Napa River, San Francisco Estuary, California, USA; 38°10' N; 122°18' W). Native species with similar trophic requirements were too few in abundance to serve as study organisms. Differences in fish diet and growth based on restoration status were expected for the more resident goby species, but not for the transient silversides. Fish were collected in June 2004 and 2005 from a 10 yr old restoring marsh, a 50 yr old restoring marsh and a natural marsh, using a modified fyke net. Diet of silversides was primarily composed of copepods, cumaceans, and flying insects, while yellowfin goby diets were composed of annelids, cumaceans, and amphipods. Prey species biomass in the stomachs of yellowfin gobies was significantly different between marshes, but these differences were not dependent on restoration status. No significant differences in Mississippi silverside growth rates were detected, and yellowfin goby growth rates varied somewhat between marshes and years, but were not significantly different between restored versus reference sites. Based on these findings, we suggest that adequate prey abundance and prey species composition is available for these fish species in both our restored and natural study sites. It also appears that some restoring breached wetlands can quickly (within 10 yr) provide equivalent habitat to natural areas, at least for generalist, non-native fishes; however, consideration of underlying mechanisms of restoration will be important in designing wetlands that specifically favor native fish populations. KEY WORDS: Acanthogobius flavimanus · Menidia audens · Wetland restoration · Non-native species · Fish ecology · Tidal marsh Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 368: [241][242][243][244][245][246][247][248][249][250][251][252][253][254] 2008 cisions in highly altered ecosystems. Fish growth and condition are seldom criteria for evaluating restoration success despite the fact that the recovery of local fish populations is a common restoration target.Effective restoration efforts require an understanding of not only the abundance of fishes in the restored habitats, but also of the quality of the habitat and its relationship to the growth and health of the species. It is necessary to consider important trophic and food web interactions, such as those between fish and prey (i.e. zooplankton) in shallow and wetland restoration (Perrow et al. 1999). Studies have shown that many salt marsh organisms benefit from trophic subsidies of organic matter originating in adjacent upland and open water habitats (Weinstein et al. 2005). Thes...