Rapid human population growth and an associated increase in consumptive water demands within the ecologically diverse Apalachicola-Chattahoochee-Flint (ACF) River basin of the southeastern United States have led to a series of highly publicized water wars, exacerbated by recent drought conditions, between the states of Alabama, Georgia, and Florida. A key issue is how managing riverine flows to meet human water needs will affect the viability of species that are federally listed as threatened or endangered, including the Gulf of Mexico sturgeon Acipenser oxyrinchus desotoi. Our present understanding of Gulf sturgeon ecology within the Apalachicola River basin indicates that altered riverine flow regimes may affect spawning success and possibly the recruitment patterns of the population. Through intensive field work, we documented Gulf sturgeon spawning site selection in the Apalachicola River and then evaluated the relationship between river stage and the available spawning habitat at these sites. We then used an agestructured simulation model to assess the effects of changes in recruitment patterns on population viability using hypothetical scenarios based on changes in flow regime and its effect on available spawning habitat. Over 3 years we were able to collect almost 500 Gulf sturgeon eggs in the Apalachicola River at three different spawning sites. We observed that the depths and flows where eggs were found were similar across years and sites despite varying river conditions. River discharges of less than 142 m 3 /s at Jim Woodruff Lock and Dam significantly reduced the spawning habitat available to Gulf sturgeon at all known spawning sites,

High human demand for limited water resources often results in water allocation trade-offs between human needs and natural flow regimes. Therefore, knowledge of ecosystem function in response to varying streamflow conditions is necessary for informing water allocation decisions. Our objective was to evaluate relationships between river flow and fish recruitment and growth patterns at the Apalachicola River, Florida, a regulated river, during 2003-2010. To test relationships of fish recruitment and growth as responses to river discharge, we used linear regression of (i) empirical catch in fall, (ii) back-calculated catch, via cohort-specific catch curves, and (iii) mean total length in fall of age 0 largemouth bass Micropterus salmoides, redear sunfish Lepomis microlophus and spotted sucker Minytrema melanops against spring-summer discharge measures in Apalachicola River. Empirical catch rates in fall for all three species showed positive and significant relationships to river discharge that sustained floodplain inundation during spring-summer. Back-calculated catch at age 0 for the same species showed positive relationships to discharge measures, but possibly because of low sample sizes (n = 4-6), these linear regressions were not statistically significant. Mean total length for age 0 largemouth bass in fall showed a positive and significant relationship to springsummer discharge; however, size in fall for age 0 redear sunfish and spotted sucker showed no relation to spring-summer discharge. Our results showed clear linkages among river discharge, floodplain inundation and fish recruitment, and they have implications for water management and allocation in the Apalachicola River basin. Managed flow regimes that reduce the frequency and duration of floodplain inundation during spring-summer will likely reduce stream fish recruitment.

We built a simulation model to assess the performance of catch‐curve residuals as an index of year‐class strength for a short‐lived and a long‐lived fish life history type across a range of assumed values for the variation in recruitment (CVR) and fishing mortality (CVF). The magnitude of CVR strongly influenced the utility of catch‐curve residuals in assessing year‐class strength. The probability of finding a significant correlation between catch‐curve residuals and true recruitment values exceeded 0.9 when CVR was greater than 0.5 for the long‐lived and greater than 1.0 for the short‐lived life history types. This suggests that larger recruitment values have a greater probability of being successfully “tracked” through the age structure. Conversely, the magnitude of interannual variation in fishing mortality weakly influenced the performance of catch‐curve residuals. The inspection of individual catch‐curve residuals relative to the known recruitment values that produced them showed considerable scatter, indicating that the utility of this metric in assessing individual year‐class strength is small. Sensitivity analyses showed that the performance of catch‐curve residuals improved modestly with equal sampling vulnerability across ages and decreased slightly with increased fishing mortality. Our results suggest that catch‐curve residuals can serve as a rudimentary measure of recruitment under ranges of recruitment and mortality variation similar to those frequently observed in field studies.

Measuring fishing effort is a common practice in fisheries management. Traditional access‐point or roving creel surveys rely on in‐person interaction between management agency personnel and anglers, the cost of which can restrict where and when the surveys can be performed. Increasing the efficiency of the techniques that are used to estimate recreational fishing effort would benefit management agencies by reducing costs or allowing for sampling at more waterbodies. We investigated using motion‐triggered game cameras installed at boat ramps to capture the number of fishing trips, number of anglers, and trip durations to be used in estimating fishing effort. We tested boat ramp cameras at five lakes in the Florida Panhandle and peninsular Florida having diversity in their fisheries and user‐group characteristics and ranging from small (<300 ha) to large (>12,000 ha). On three of the lakes, we concurrently conducted roving creel surveys, allowing us to compare the methods’ estimates of fishing effort, costs, and personnel time. The camera‐based estimates of fishing effort were similar to those from the roving creel survey but tended to exceed them, including up to a factor of 2.22 in one case. These differences in effort estimates may have been due to several things such as erroneously designating some nonfishing trips as fishing trips during photo analysis, overestimating time spent fishing by ascribing all of the time between launch and retrieval to fishing, or underestimating fishing effort via roving creel surveys, as creel clerks might have occasionally missed anglers during the angler counts. Roving creel surveys were 1.25–2.50 times as expensive as camera counts because the cameras required less personnel effort. The detection probabilities that were calculated from the camera results ranged from 0.57 to 1.00, but the value was ≥ 0.86 at four of the five lakes. Despite some challenges, boat ramp cameras provided an effective, cost‐beneficial tool for estimating fishing effort.

Abundance of the spotted sunfish Lepomis punctatus has been positively correlated with interannual fluctuations in river stage, making this a potential indicator species for streamflow management. We evaluated patterns of habitat selection by adult and juvenile spotted sunfish and related them to simulated declines in river stage at three southwestern Florida rivers (Anclote, Little Manatee, and Manatee rivers). To identify habitat selection patterns, we used multivariate analysis of variance to compare measured characteristics (i.e., current velocity, depth, and cover abundance) of habitats used by spotted sunfish with those of randomly located habitats within the stream margin environment. Spotted sunfish generally selected habitats with greater structural complexity than the average available habitat. In many instances, spotted sunfish appeared to select habitats that contained both large and fine woody debris. However, fish were collected from a variety of habitat types during the study, indicating that this species is somewhat general in its habitat use. We found few significant differences in habitat measures between juvenile and adults, suggesting that habitat selection was similar between these life stages. Our model simulations indicated that 0.3‐m reductions in average daily river stage could reduce habitat availability for spotted sunfish by 20‐70% across systems. Spotted sunfish used habitats with greater‐than‐average resiliency to stage declines (i.e., deeper, more complex habitat). Considering that even minor reductions in the average daily stage during fall and spring could substantially reduce overall availability of suitable habitat, the inundation of complex habitat types is probably important for spotted sunfish.