Connectivity and Estuaries: Historically, estuarine fisheries biology has focused on the theme of estuarine dependency, with an emphasis on microhabitat use. Ironically, however, few fishes that we associate with estuaries are in fact obligatory users (anadromous fishes are a notable exception). What then are the causes and consequences of estuarine habitat vs. coastal habitat use? To address this issue, we investigate "connectivity" in the life cycles of fishes. Connectivity here refers to the dependence of fish production and population dynamics on dispersal and migration among multiple habitats. We are especially interested in migration and habitat use as behaviors that control and regulate population dynamics, and cause individuals to be differentially vulnerable to exploitation and pollution. An strong emphasis in our laboratory (developed through past support by National Science Foundation) is to use otolith tracers to reconstruct habitat histories and nursery use in estuarine and coastal fishes. Still, because migration and dispersal are complex in measurement, we utilize a battery of approaches.
An example of otolith tracers in a striped bass otolith .... This X-ray map image shows evidence of early exploration of marine habitats by Hudson River striped bass, followed my annual spawning migrations into low salinity environments (red = high strontium levels)
The Contingent Hypothesis: The concept of closed population
structure - the unit stock concept - has been fundamental to marine
fisheries science for nearly a century (Secor 2002). We have argued
that anomalous individual migration and habitat use patterns - those
that diverge from expected ontogenetic circuits of migration - represent
modalities, and that these modalities confer resiliency in populations
where mortality risk and production is related to specific spatial
behaviors (Secor et al. 2009; Kerr et al. 2010; Petitgas et al. 2010), and are otherwise known as partial migration (Secor and Kerr 2009). These modalities are well represented by the retentive and
migratory forms of salmon and chars, but have been observed increasingly
in marine and coastal fishes through the use of otolith microchemistry
(Secor 1999; Secor and Kerr 2009). Groups of individuals with similar migration trajectories
are called contingents, a term coined initially by Hjort (1914).
The prevalence of contingent behaviors provides insight into the
evolution of estuarine dependency, as well as the consequences of
patterns of estuarine dependency to population dynamics and pollution
ecology. We are actively testing hypotheses that can explain contingent
structure and its consequences, using white perch as a model species. Current research supported by Maryland Sea Grant seeks to determine if striped bass exhibit partial migration patterns similar to white perch.
An example of contingent structure .... Two otolith strontium x-ray maps from white perch young-of-the-year (YoY) juveniles, one giving evidence of freshwater residency during its first year of life (blue), and another exhibiting dispersal to brackish habitats (green)
Kerr, L.A. and D.H. Secor. 2012. Partial migration across populations of white perch (Morone americana): a flexible life history strategy adapted for persistence in a variable estuarine environment. Estuaries and Coasts 35: 227-336.
Williams, E.P., A.C. Peer, T.J. Miller, D.H. Secor, and A.R. Place. 2012. A phylogeny of the temperate sea basses (Moronidae) characterized by a translocation of the mt-ND6 gene. Journal of Fish Biology 80: 110-130.
Wingate, R.L., D.H. Secor, and R.T. Kraus. 2011. Patterns of striped bass residence and migration in a sub-estuary of the Chesapeake Bay. Transactions of the American Fisheries Society 140: 1441-1450.
Petitgas, P., D.H. Secor, I. McQuinn, G. Huse, and N. Lo. 2010. What is a collapsed stock and what is required for its recovery? Mechanisms that sustain and establish life-cycle closure in space and time. ICES J. Marine Science 67: 1841-1848.
Secor, D.H. 2010. Is otolith science transformative? New views on fish migration. Environ. Biol. Fishes 89: 209-220.
Kerr, L.A., S.X. Cadrin, and D.H. Secor. 2010. Simulation modeling as a tool for examining the consequences of spatial structure and connectivity to local and regional population dynamics. ICES J. Mar. Sci.67: 1631-1639.
Kerr, L.A. and D.H. Secor. 2010. Latent effects of early life history on partial migration for an estuarine-dependent fish. Environ. Biol. Fishes 89: 479-492.
Niklitschek, E.J., D. H. Secor, A. Lafon, P. Toledo, M. George-Nascimento. 2010. Segregation of SE Pacific and SW Atlantic blue whiting stocks: evidence from complementary otolith microchemistry and parasite assemblages. Environ. Biol. Fishes 89: 399-413.
Kerr, L.A., S.X. Cadrin, and D.H. Secor. 2010. The role of spatial dynamics in the stability, resilience, and productivity of fish populations: An evaluation based on white perch in the Chesapeake Bay. Ecological Applications 20: 497-507.
Cairns, D.K., D.H. Secor, W.E. Morrison, and J.A. Hallet. 2009. Salinity-linked growth in anguillid eels and the paradox of temperate-zone anadromy. J. Fish Biol. 74: 2094–2114
Kerr, L.A., Piccoli, P.M. & Secor, D.H. 2009. Partial migration as exemplified by the estuarine-dependent white perch. Fisheries 34 (3): 114-123.
Secor, D.H., Kerr, L.A. and Cadrin, S.X. 2009. Connectivity effects on productivity, stability, and persistence in an Atlantic herring metapopulation. ICES J. Mar. Sci. 66: 1726-1732
Kerr, L.A. and D.H. Secor. 2009. Bioenergetic trajectories underlying partial migration in Patuxent River (Chesapeake Bay) white perch (Morone americana). Can. J. Fish. Aquat. Sci. 66: 602-612.
Cadrin, S.X. and D.H. Secor. 2009. Chapter 22, p. 405-426. Accounting for spatial population structure in stock assessment: past, present and future. In R.J. Beamish and B.J. Rothschild (eds.) Future of Fishery Science in North America. 405 Fish & Fisheries Series, Springer Science.
Secor, D.H. and P.M. Piccoli. 2007. Determination of frequency of anadromous migrations by Chesapeake Bay striped bass based upon otolith microchemical analysis. Fisheries Bulletin 105: 62-73.
Secor, D.H. 2007. The year-class phenomenon and the storage effect in marine fishes. J. Sea Res. 57: 91-103.
Secor, D.H. and J.R. Rooker. 2005. Connectivity in the life histories of fishes that use estuaries. Introduction to series of papers. Estuarine, Coastal, and Shelf Science 64: 1-4.
Kraus, R.T. and Secor, D.H. 2005. Evaluation of connectivity in estuarine-dependent white perch populations of Chesapeake Bay. Estuarine and Coastal Shelf Science. 64: 94-107.
Kraus, R.T. and Secor, D.H. 2004. The dynamics of white perch (Morone americana Gmelin) population contingents in the Patuxent River Estuary, Maryland USA. Marine Ecology Progress Series. 279: 247-259.
Secor, D.H. 2004. Fish migration and the unit stock: three formative debates, p. 17-44. In Steven X. Cadrin, Kevin D. Friedland, John R. Waldman (ed.s). Stock Identification Methods. Elsevier Inc., Burlington.
Secor, D. H. 2002. Estuarine dependency and life history evolution in temperate sea basses. Fisheries Science 68: (Suppl. 1): 178-181.
Secor, D.H. 2002. Historical roots of the migration triangle. ICES J. Mar. Sci. 215:329‑335.
Secor, D.H., J.R. Rooker, E. Zlokovitz and V.S. Zdanowicz. 2001. Identification of riverine, estuarine, and coastal contingents of Hudson River striped bass based upon otolith elemental fingerprints. Mar. Ecol. Progr. Ser. 211: 245-253.
Secor, D.H. 1999. Specifying divergent migration patterns in the concept of stock: The Contingent Hypothesis. Fish. Res. 43: 13-34.
Kerr, L.A., R.T. Kraus, and D.H. Secor. 2007. Stable isotope (δ13C and δ18O) composition of otoliths as a proxy for environmental salinity experienced by an estuarine fish. Mar. Ecol. Progress Series 348: 245-253.
Elsdon, T.S., Wells, B.K., Campana, S.E., Gillanders, B.M., Jones, C.M., Limburg, K.E., Secor, D.H., Thorrold, S.R., and Walther, B.D. 2008. Otolith chemistry to describe movements and life-history parameters of fishes: hypotheses, assumptions, limitations and inferences using five methods. Oceanography and Marine Biology: An Annual Review 46: 207-330.
Kraus, R.T. and D.H. Secor. 2004. Partitioning of strontium in otoliths of estuarine fishes: experimentation in a model system, white perch Morone americana (Gmelin). J. Exp. Mar. Biol. Ecol. 302: 85-106
Rooker, J.R., R.T. Kraus, and D.H. Secor. 2004. Dispersive behaviors of black drum and red drum: Is otolith Sr:Ca a reliable indicator of salinity history. Estuaries 27: 334-341.
Kraus, R.T., and D.H. Secor. 2003. Otolith Sr:Ca response to a manipulated environment in young American eels. Am. Fish. Soc. Symp. 33: 79-85.
Secor, D.H. and J.R. Rooker. 2000. Is otolith strontium a useful scalar of life-cycles in estuarine fishes? Fish. Res. 46(1-3): 359-371.
Kimura, R, D.H. Secor, E.D. Houde and P.M. Piccoli. 2000. Up-estuary dispersal of young-of-the-year bay anchovy Anchoa mitchilli in the Chesapeake Bay: Inferences from microprobe analysis of Sr in otoliths. Mar. Ecol. Progr. Ser. 208: 217-227.
Secor, D.H., T. Ota and M. Tanaka. 1998. Use of otolith microanalysis to determine estuarine migrations of Ariake Sea Japanese seabass. Fish. Sci. 64: 740-743.
Secor, D.H. and P. M. Piccoli. 1996. Age- and sex-dependent migrations of the Hudson River striped bass population determined from otolith microanalysis. Estuaries 19: 778-793.
Secor, D.H., A. Henderson-Arzapalo and P.M. Piccoli. 1995.
Can otolith microchemistry chart patterns of migration and habitat
utilization in anadromous fishes? J. Exp. Mar. Biol. Ecol. 192: 15-33.
Secor, D. H. 1992. Application of otolith microchemistry analysis to investigate anadromy in Chesapeake Bay striped bass. Fish. Bull. 90(4):798-806.
Arslan, Z. and Secor, D.H. 2005. Analysis of trace transition elements and heavy metals in fish otoliths as tracers of habitat use by American eels in the Hudson River estuary. Estuaries. 28: 382-393.
Ashley, J.T.F, D.H. Secor, E. Zlokovitz, J.E. Baker and S.Q. Wales. 2000. Linking habitat use of Hudson River striped bass to accumulation of polychorinated biphenyl congeners. Environ. Sci. Techn. 34: 1023-1029.
Zlokovitz, E.R. and D.H. Secor. 1999. Effect of habitat use on PCB body burden in Hudson River striped bass (Morone saxatilis). Can. J. Fish. Aquat. Sci. 56 (Suppl.1): 86-93.