Alford J.B.,Fisheries Management Section |
Alford J.B.,University of Tennessee at Knoxville
Hydrobiologia | Year: 2014
This study determined if a spatial hierarchy existed with respect to reach-scale habitat, subwatershed-scale, and watershed-scale geomorphology and land use stressors on fish assemblages in southeastern U.S. coastal plain streams. During May-October 2009-2012, fishes were sampled by seine, and habitat was assessed at 50 reaches in the Lake Pontchartrain Basin (USA). Using partial redundancy analysis (pRDA) a variance decomposition procedure was used to partial out influences of confounding covariables at each spatial scale. Reach-scale habitat had the strongest association with the assemblage. Stream width, depth, aquatic vegetation and human debris cover, rapid habitat assessment score, and large woody debris volume were the most important variables. At subwatershed and watershed scales, natural and anthropogenic characteristics were important, including elevation, gradient, watershed area, wetland cover, stream density, road, dam and oil/gas well densities. Six species were associated most strongly with the watershed variables, compared to reach- and subwatershed-scale variables. These species had more "r-selected" life-history strategies (e.g., smaller eggs, shorter life spans, multiple broods, longer spawning season, and trophic generalists). In contrast, most species that were associated strongest with reach-scale variables exhibited more "k-selected" life-history traits (e.g., larger eggs, longer life spans, shorter spawning season, single brood, and trophic specialists). © 2014 Springer International Publishing Switzerland.
Hakala J.P.,Fisheries Management Section |
Sammons S.M.,Auburn University
Fisheries Management and Ecology | Year: 2015
Alabama bass, Micropterus henshalli Hubbs & Bailey, are the dominant sportfish of Allatoona Reservoir, Georgia, USA, but no population assessment has been conducted. Thus, growth and total annual mortality were estimated in spring 2005, and a tagging study was conducted in 2006 and 2007 to estimate angler exploitation. These data were used with an age-structured model to assess performance of a 356-mm minimum length limit (MLL), a 406-mm MLL and a 330- to 406-mm protected slot length limit (SLL) compared to the present harvest regulation of no MLL. Mean annual exploitation varied from 12 to 22% each year and was generally highest for fish > 330 mm; total annual mortality was 44%. Models predicted a 49-153% increase in numbers of Alabama bass reaching 432 mm, a 22-66% decline in numbers harvested and only moderate declines in yield (5-25%) with the alternative harvest regulations compared to current conditions. The SLL may be an acceptable compromise to allow Allatoona Reservoir anglers to still harvest fish while also improving Alabama bass size structure. © 2015 John Wiley & Sons Ltd.
Albanese B.,Nongame Conservation Section |
Litts T.,Fisheries Management Section |
Camp M.,Tennessee Technological University |
Weiler D.A.,Nongame Conservation Section
Ecology of Freshwater Fish | Year: 2014
The goldline darter (Percina aurolineata) is threatened by recent increases in urbanisation in the Coosawattee River watershed, but no studies have addressed their current status. Similarly, limited data on habitat use make it difficult to understand factors that may impact this species. We compared occurrence data before (1996-2000) and after (2009-2011) a period of rapid development and population growth within the watershed. Single-season occupancy models were built to account for imperfect species detection and to identify habitat covariates. MaxEnt was used to identify important stream reaches for conservation and to understand landscape scale factors correlated with the distribution of goldline darters. Our results indicate a high proportion of sites occupied upstream of Carters Lake during the historic and recent time periods, with no evidence of decline. However, occurrences of goldline darters for sites in Talking Rock Creek and the lower Coosawattee River were sparse in the historic period and absent during the recent period. The probability of detecting goldline darters is low and was positively associated with the occurrence of small substrate. Species distribution models were strongly influenced by watershed area and elevation and indicated a high probability of suitable habitat within the Coosawattee River and large tributaries upstream of Carters Lake. While goldline darter occupancy is currently stable upstream of Carters Lake, continued urbanisation is a threat to long-term persistence. We recommend additional monitoring and describe a protocol that allows for precise estimates of species occupancy while minimising the risk of sampling-related mortality. © 2013 John Wiley & Sons A/S.