Density-dependent regulation of year-class strength in age-0 juvenile striped bass (Morone saxatilis)

Abstract

Abundance of age-0 striped bass ( Morone saxatilis ) exhibits 50-fold variability in Chesapeake Bay. Processes that act to reduce and thus regulate this variability were investigated. The potential for density-dependent regulation of growth and mortality in the early juvenile stage and its causes were investigated. Data from multiple seine and trawl surveys in upper Chesapeake Bay and tributaries were analyzed to construct growth and mortality indices having a high degree of spatial and temporal resolution. Age-0 mean lengths in September were inversely related to density, ranging from 67.8 mm in 1994, when mean density was 0.036·m–2, to 104.5 mm in 1992, when mean density was 0.003·m–2. Except for the Potomac River, evidence for density-dependent growth was consistent across subpopulations. Bioenergetics modeling indicated that prey consumption was limiting except in low-abundance years. Mortality increased with respect to abundance and also was density-dependent. The significant interaction between age-0 juvenile length in September and subsequent winter temperature on mortality indicated that density-dependent growth leads to size-selective overwinter mortality. A statistical model including age-0 abundances, age-0 lengths, and winter temperature explained a substantial fraction of variability and the mechanisms for regulation of striped bass recruitment.

Density-dependent habitat use and growth of an estuarine fish

“…Alternatively, our results are more consistent with a recent body of work suggesting that estuarine organisms are not immune to density-dependent effects (e.g., Buckel et al 1999;Craig et al 2007;Martino and Houde 2012). For instance, Craig et al (2007) documented reductions in growth and increased mortality in high density treatments of spot (Leiostomus xanthurus).…”

“…Also, estuarine systems are not as amenable to study as coral reefs or small streams because (i) water clarity is often very low in estuaries, so following the fates of individuals using visual assessment is often not possible, (ii) estuarine fishes are generally not site-attached, so manipulative experiments are rarely possible, (iii) estuaries tend to be heavily fished, (iv) estuaries have highly variable environmental conditions, and (v) spatially and temporally extensive fishery-independent data sets are less common in estuaries. Despite these difficulties, some studies have highlighted the importance of densitydependent growth, mortality, or dispersal for estuarine organisms (e.g., Buckel et al 1999;Cowan et al 2000;Martino and Houde 2012). The majority of these studies have related individual growth rates or loss rates to annual density estimates; however, there has been little attention paid to the ways in which annual density in combination with densityindependent factors influence spatial redistribution patterns of estuarine organisms.…”

Multi-decadal variation in size of juvenile Summer Flounder (Paralichthys dentatus) in Chesapeake Bay

“…Indeed, densitydependent size variations have been documented for juvenile estuarine fishes including American Shad Alosa sapidissima (Tuckey 2009), Striped Bass Morone saxatilis (Martino & Houde 2012), Spot Leiostomus xanthurus (Craig et al 2007), and European Plaice Pleuronectes platessa (Pihl et al 2000, Geffen et al 2011. In habitats where size-selective predation is an important component of juvenile mortality, larger individuals are more likely to survive than smaller ones (Miller et al 1988, Witting & Able 1993, Sogard 1997) and larger individuals may therefore make a greater contribution to year-class strength (Houde 2008).…”

“…Chlorophyll-a sampling locations represent fixed stations monitored by the Chesapeake Bay Program. Daily surface chlorophyll-a values from these stations were interpolated from monthly monitoring data for June toNovember, 1988to 2012.…”

Striped Bass Early Life History in the Macrotidal Shubenacadie River

“…By comparison, in five of six tributaries to Chesapeake Bay the growth of age‐0 Striped Bass was inversely related to juvenile abundance, suggesting that food was a limiting factor. The one river in which density dependency was not evident, the Potomac River, had a substantially higher prey availability (Martino and Houde ).…”