Abstract
Largemouth bass (LMB; Micropterus salmoides) recruitment is limited by a critical developmental period during early life stages, but this mechanism may be less important within non-native habitats. We conducted boat electrofishing surveys in four tidal lakes of California’s Sacramento–San Joaquin Delta (SSJD) from 2010 to 2011 to describe introduced LMB recruitment dynamics. We evaluated growth, proximate composition, and health indices of young-of-the-year (YOY) LMB among tidal lakes and developed an integrated count model to determine how factors known to affect LMB recruitment shape SSJD population structure. Our results show a mismatch among growth, nutrition, and YOY abundance, where the tidal lake with the most abundant and fastest-growing LMB had the poorest nutritional status. The warm winter water temperatures and lack of a hatching-cohort growth advantage suggests overwinter starvation plays a less important role in SSJD LMB recruitment than in many native LMB habitats. Collectively, our results suggest that habitat characteristics (submerged aquatic vegetation) and not overwinter mortality shapes SSJD LMB population structure, a mechanism consistent with contemporary hypotheses about the altered fish community structure of the SSJD.
Highlights
The largemouth bass (LMB; Micropterus salmoides) is an apex predator native to drainages of the eastern and Gulf coasts of the United States and has been introduced to many locations throughout the world to support recreational fisheries (Cambray 2003; Maezono et al 2005; Takamura 2007)
Insufficient growth and fat storage have been implicated as a major source of mortality during early Largemouth bass (LMB) life stages (Miranda and Hubbard 1994a; Ludsin and DeVries 1997; Garvey et al 1998); LMB cohort strength can be established by other sources of mortality (e.g., predation and refugia provided by submerged aquatic vegetation (SAV); Miranda and Hubbard 1994b; Rogers and Allen 2009)
We used a combination of growth and health metrics, along with a relatively novel size-structured integrated abundance model to investigate whether the common mechanisms that limit LMB cohort strength within their native range limit LMB populations within the Sacramento–San Joaquin Delta (SSJD)
Summary
The largemouth bass (LMB; Micropterus salmoides) is an apex predator native to drainages of the eastern and Gulf coasts of the United States and has been introduced to many locations throughout the world to support recreational fisheries (Cambray 2003; Maezono et al 2005; Takamura 2007). Year-class strength for LMB is often determined by a “critical period” associated with growth in early life stages (Hjort 1914; Houde 2008; Ludsin and DeVries 1997). Insufficient growth and fat storage have been implicated as a major source of mortality during early LMB life stages (Miranda and Hubbard 1994a; Ludsin and DeVries 1997; Garvey et al 1998); LMB cohort strength can be established by other sources of mortality (e.g., predation and refugia provided by submerged aquatic vegetation (SAV); Miranda and Hubbard 1994b; Rogers and Allen 2009).
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