Technological advances represent opportunities to enhance and supplement traditional fisheries sampling approaches. One example with growing importance for fisheries research is hydroacoustic technologies such as side‐scan sonar. Advantages of side‐scan sonar over traditional techniques include the ability to sample large areas efficiently and the potential to survey fish without physical handling—important for species of conservation concern, such as endangered sturgeons. Our objectives were to design an efficient survey methodology for sampling Atlantic Sturgeon Acipenser oxyrinchus by using side‐scan sonar and to develop methods for analyzing these data. In North Carolina and South Carolina, we surveyed six rivers thought to contain varying abundances of sturgeon by using a combination of side‐scan sonar, telemetry, and video cameras (i.e., to sample jumping sturgeon). Lower reaches of each river near the saltwater–freshwater interface were surveyed on three occasions (generally successive days), and we used occupancy modeling to analyze these data. We were able to detect sturgeon in five of six rivers by using these methods. Side‐scan sonar was effective in detecting sturgeon, with estimated gear‐specific detection probabilities ranging from 0.2 to 0.5 and river‐specific occupancy estimates (per 2‐km river segment) ranging from 0.0 to 0.8. Future extensions of this occupancy modeling framework will involve the use of side‐scan sonar data to assess sturgeon habitat and abundance in different river systems. Received January 15, 2013; accepted June 10, 2013
In 2012, the National Oceanic and Atmospheric Administration (NOAA) declared Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus to be threatened or endangered throughout its range in U.S. waters. Restoration of the subspecies will require much new information, particularly on the location and timing of spawning. We used a combination of acoustic telemetry and sampling with anchored artificial substrates (spawning pads) to detect fall (September–November) spawning in the Roanoke River in North Carolina. This population is included in the Carolina Distinct Population Segment, which was classified by NOAA as endangered. Sampling was done immediately below the first shoals encountered by anadromous fishes, near Weldon. Our collection of 38 eggs during the 21 d that spawning pads were deployed appears to be the first such collection (spring or fall) for wild‐spawned Atlantic Sturgeon eggs. Based on egg development stages, estimated spawning dates were September 17–18 and 18–19 at water temperatures from 25.3°C to 24.3°C and river discharge from 55 to 297 m3/s. These observations about fall spawning and habitat use should aid in protecting critical habitats and planning research on Atlantic Sturgeon spawning in other rivers. Received April 14, 2014; accepted September 9, 2014
Stocking of trout to support recreational fisheries is a common practice among state and federal agencies to meet angling and harvest demands. Success of stocking efforts relies upon fish behavior and survival to maximize the availability of fish to anglers. We quantitatively described the movement behavior and survival of stocked Brook Trout Salvelinus fontinalis, Brown Trout Salmo trutta, and Rainbow Trout Oncorhynchus mykiss in three southern Appalachian Mountain streams in western North Carolina, USA, that were managed under delayed harvest regulations. Hatchery trout were tagged with a combination of PIT tags and radio transmitters (radio tags); stocked into "Delayed Harvest Trout Waters" of the North Toe, East Prong Roaring, and Little rivers; and monitored during the catch-andrelease season from October to June. Assessed according to river and species, 19-65% of trout emigrated from the delayed harvest study reaches, while 1-29% died within the reaches. The majority of radio-tagged fish (71%; 59-85% by river) remained within 2 km of the stocking location, whereas 6% migrated over 10 km from the stocking location. Few trout stocked during fall (October and November) were available to anglers the following June due to a combination of migration and mortality. Emigration from delayed harvest study reaches was associated with stocking and highflow events. Multi-state modeling detailed these observations with weekly estimates of migration and survival rates. River-specific differences in emigration and mortality suggested that emigration was a greater source of trout loss than mortality in all rivers; no pattern related to river size was apparent in emigration, but mortality was greater in small streams. Brook Trout mortality rates were highest among the three species, and large fish of most species showed higher emigration and mortality than catchable-sized trout. Fisheries managers can apply our results to alter stocking regimes so as to enhance the efficiency of stocking and the acclimation of stocked trout to instream environments.
Sturgeons (Acipenseridae) are one of the most threatened taxa worldwide, including species in North Carolina and South Carolina. Populations of Atlantic Sturgeon Acipenser oxyrinchus in the Carolinas have been significantly reduced from historical levels by a combination of intense fishing and habitat loss. There is a need for estimates of current abundance, to describe status, and for estimates of historical abundance in order to provide realistic recovery goals. In this study we used N‐mixture and distance models with data acquired from side‐scan sonar surveys to estimate abundance of sturgeon in six major sturgeon rivers in North Carolina and South Carolina. Estimated abundances of sturgeon greater than 1 m TL in the Carolina distinct population segment (DPS) were 2,031 using the count model and 1,912 via the distance model. The Pee Dee River had the highest overall abundance of any river at 1,944 (count model) or 1,823 (distance model). These estimates do not account for sturgeon less than 1 m TL or occurring in riverine reaches not surveyed or in marine waters. Comparing the two models, the N‐mixture model produced similar estimates using less data than the distance model with only a slight reduction of estimated precision. Received May 3, 2014; accepted October 14, 2014
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,
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