Habitat mediation of young largemouth bass population dynamics

Abundance and distribution of age-0 largemouth bass (Micropterus salmoides) were determined in relation to characteristics of littoral habitat in a spatially and temporally heterogeneous reservoir at three landscape scales; inter-embayment, intra-embayment, and microhabitat ({dollar}<{dollar}10m). The influence of water level decline on littoral habitat and distribution patterns of age-0 largemouth bass was determined. Age-0 largemouth bass were collected via night electrofishing. Habitats (cover, substratum, slope characteristics) were measured physically or using a geographic information system (GIS). A habitat-abundance model was developed using stepwise multiple regression analysis and validated outside the intensive study area. Age-0 largemouth bass exhibited patchy distributions that were predictable using habitat parameters. Scale of investigation was critical for determining related parameters. At the inter-embayment level, substratum (gravel) and slope characteristics predicted distribution and relative abundance, while at smaller scales cover components increased precision of predictions. However, cover was negatively correlated with bass abundance at the 100 m scale and positively related to microdistribution. Amounts of habitat may impose a carrying capacity on scales from embayment to microhabitat and affect density-dependent interactions. Additionally, diel movement patterns of age-0 largemouth bass were determined using pre-positioned electrofishing grids in shoreline habitats (paired day-night design). Age-0 largemouth bass exhibited diel onshore-offshore migrations and degree of movement was mediated by cover. Age-0 largemouth bass were less likely to move offshore to diufllal habitats from nocturnal (inshore) resting habitats where cover is available. Movements likely were related to predator avoidance and foraging behavior. Minor decreases in water level (20 cm) caused severe impacts for littoral habitat mosaics (arrangement and size of patches changed) and affected distribution patterns of age-0 largemouth bass. Decreases in gravel substratum and cover components and concurrent shifts in distribution of age-0 largemouth bass were detected. The data suggest that age-0 largemouth bass distribution, abundance and movement are subject to regulation by habitat at localized landscape scales. These findings are significant for development of management and sampling strategies for this species and suggest that habitat enhancement programs may impact recruitment if conducted at the proper scale.