No description available.

Paddlefish are long-lived large river fish which are declining in many areas of their range due to habitat modifications and overfishing. A framework for management of paddlefish in Mississippi is proposed and a case study of its application to the paddlefish population of the Tennessee-Tombigbee Waterway (TTW) is presented. The framework includes four phases: (I) distribution and stock assessment; (II) determination of limiting factors; (III) design and implementation of management actions; and (IV) review and monitoring. Phase I of management in the TTW consisted of gill-net surveys in four impoundments. Paddlefish abundance was estimated at 1,581 to 8,851 in Demopolis Lake, Alabama. In Gainesville Lake, Alabama, CPUE was 16.8 times less than Demopolis Lake. No paddlefish were caught in Aliceville Lake, Mississippi/Alabama, or Columbus Lake, Mississippi. Demopolis Lake paddlefish grew faster than more northern populations, but slower than more southern populations (Lt = 971.8 [1 − e−0.2844 (t+0.6962)]) and had a high annual mortality rate (A = 0.406) comparable to other southern populations. Potential limiting factors related to spawning in Demopolis Lake and stocking programs in Columbus Lake were investigated pursuant to Phase II. Paddlefish eggs were collected in the Noxubee River and a unique flowing bendway habitat in Demopolis Lake during early April when discharge was ¡Ý2.74 m above 50% exceedance. Flow timing and magnitude in the Noxubee River was related to paddlefish year-class strength (linear regression P = 0.089; R2 = 0.830). Radio-tagged paddlefish exhibited seasonal site fidelity and 4 of 10 translocated fish returned to their area of initial capture.,Columbus Lake provides food resources and physiochemical characteristics adequate for paddlefish survival, but depth and zooplankton density are more favorable in Demopolis Lake. Emigration of stocked juvenile paddlefish was low in Columbus Lake habitats; survival (percent after one month ¡À SE) was 5 ¡À 5 in backwaters and 28 ¡À 9 in the mainstem after one month. Phase III recommendations include further investigation of early life history requirements and protection of bendway and tributary habitat in Demopolis Lake. The annual stocking of 4,000 juvenile paddlefish in the mainstem of Columbus Lake and up to 1 million larval paddlefish in a tributary is recommended.

No description available.

Substrate composition plays a critical role in determining the spawning success of Atlantic sturgeon. A benthic analysis of the tidal freshwater portion of the James River, Virginia, was performed to locate and protect remaining sturgeon spawning habitat within the James River system. I modeled structural habitat, substrate distribution, and river bathymetry from Richmond, Virginia to the Appomattox River confluence. A classification model was developed to describe the dominant substrate type (mud/silt, sand, gravel, bedrock) using side scan sonar data collected from August 2011-Febuary 2012. River depth, bottom imagery, substrate density (hardness), and ground truth substrate samples were interpolated into a GIS model to spatially describe and quantify essential sturgeon spawning habitat. Finally, I attempted a change analysis of historical substrate composition throughout the study area. Gravel, cobble, and bedrock, swept clean of silt or mud, was deemed a hard bottom substrate suitable for spawning success. Mud and silt dominated the vast majority of river substrate, representing approximately 67 % of river bottom surveyed. Sand comprised 17 % of river bottom, gravel represented 11 % and bedrock represented 5 %. Sixteen percent of the reach was hard bottom habitat consisting of a bed substrate dominated by gravel, cobble, or bedrock. Regions of hard bottom habitat found at depths ≥ 10 m were selected to model essential sturgeon spawning habitat. The river bottom within the reach contained approximately 8 % essential spawning habitat. The majority of hard bottom habitat was located in major bends of the river where scouring occurs. The historical comparison of available hard bottom habitat identified a 28 % loss of hard bottom since 1853. The greatest losses in hard bottom occurred in the upper portions of the study area (55 % loss in hard bottom habitat). Hard bottom habitat lost in the lower portion of the study area was partially offset by the creation of new hard bottom habitat within the narrow channel cuts bypassing Jones Neck and Turkey Island. Historical comparison of the Hatcher Island, Turkey Island, and Jones Neck oxbows identified heavy siltation and reduced depths likely due to anthropogenic alterations in the meander bends linked to shipping channel creation. The altered flow regime has resulted in increased sedimentation and has drastically reduced available hard bottom substrate within the natural channel of Jones Neck and Turkey Island. The increased availability of hard bottom habitat within the confines of the shipping channel has indicated that the alteration of the river bottom, through flow modification and dredging practices, may have replaced a portion of lost historical spawning habitat. Fisheries managers could use the data from the substrate analysis to better understand and protect essential areas necessary for Atlantic sturgeon spawning success.

Pacific cod (Gadus macrocephalus) is an important species, both economically and ecologically in the Bering Sea and Aleutian Islands (BSAI). However, little is known about its spawning dynamics. To address this knowledge gap, I developed a gross anatomical maturity key for Pacific cod to assess temporal and spatial patterns of reproductive maturity. Gross anatomical maturity keys estimate reproductive maturity by categorizing changes that occur in appearance of ovaries during maturation. Because maturity keys are based on characteristics that change on a continuum, stage assignment can be subjective particularly for ovaries in transition (displaying characteristics of more than one stage). Histological processing is often used to verify maturity key staging by estimating the maturity of individual oocytes from within assessed ovaries. I compared individual oocyte development through histological processing with gross anatomical stage assignments to evaluate the accuracy of Pacific cod maturity key using two approaches. First, assumptions made in delineating advancing characteristics between stages during the development of the key were analyzed by comparing oocyte development from ovaries assigned to key maturity stages by the researchers who designed the key. Secondly, the consistency in the use of the maturity key was addressed by comparing stage assignments to oocyte development for multiple data collectors employing the maturity key in the field. Misclassification rates for the key designers were 22% and field samplers using the key resulted in misclassification rates of 43%. While the misclassification rates are high, the mismatch between histological assessments and gross maturity was very narrow and most often assigned correctly to an adjacent stage. Misclassifications occur most often in the vitellogenin stages where criteria for delineating between stages both histologically and through the use maturity key are based on relative changes in size and color of the ovaries. By using morphological changes to track ovarian maturation, gross anatomical maturity keys provide an easily applied and inexpensive method for the collection of large quantities of data. Maturity data collected by observers aboard commercial fishing vessels in the BSAI were used to construct maps showing spawning sites along the continental shelves of the BSAI between the 100 and 200m isobaths. Spawning stage data for days where a high percentage of spawning was observed ("hot days") were mapped to show areas of high intensity spawning ("hot spots"). Hot spots were identified north of Unimak Island, in the vicinity of the Pribilof Islands, at the shelf break near Zhemchug Canyon, and adjacent to the central and western Aleutian Islands. Further analysis of spawning and spent stage data suggests spawning phenology was consistent during the three study years with varying climate conditions, though variation was seen in the duration of the spawning season among years and regions within years. While the processes determining the timing and location of spawning are poorly understood, knowledge of the above patterns allows further examination of how Pacific cod spawning correspond with environmental conditions throughout the season and between years of varying climate patterns. This work provides an initial description of the distribution and phenology of Pacific cod spawning along with a generalized description of oceanographic features observed at hot spot locations during the spawning season. / Graduation date: 2013

Lake trout (Salvelinus namaycush) have a broad distribution across Canada’s north, yet most studies that describe reproductive habitat and behaviour have been conducted in the southern extent of their range. Northern regions are experiencing unprecedented changes from climate and industrial development, and thus there is a pressing need to understand the reproductive habitat and behaviour of this species. I examined a dozen sites around Alexie Lake, Northwest Territories, to test if physical habitat and wind exposure were important determinants of spawning site use and embryonic survival. Spawning was found to occur in ~2 m water depth, on 3–15 cm diameter clean substrate on the leading edge of shoals that ended in a rock crib rising abruptly in nearshore regions around the lake. Wind direction was predominantly from the west, although it was highly variable within and among spawning seasons. I found evidence of lake trout spawning at each site examined, which was not limited to shoals facing a predominant wind direction. High variation in embryonic survival (2–83%) from incubation trays was observed among spawning sites, demonstrating a large gradient in habitat quality exists within a given lake. However, modelled wind exposure did not predict embryonic survival, nor did physical characteristics - including shoal depth and slope, as well as cobble size and shape - that may influence interstitial water flow on spawning shoals. Using an acoustic telemetry monitoring system and novel spatial temporal clustering analysis, I was able to quantify lake trout spawning movements and behaviours over the course of an entire spawning season. Lake trout formed clusters on spawning shoals around the entire nearshore region, as well as around several islands, confirming that suitable spawning habitat is abundant in Alexie Lake. Males arrived on spawning shoals earlier than females and remained longer for a maximum of 25 consecutive days; females occupied spawning shoals for a maximum of 8 consecutive days over the course of the spawning season. Males formed over four times as many spawning clusters and visited twice as many sites than females. Spawning clusters were predominantly formed at night but were also observed during daylight hours, especially during the peak spawning season (September 9–19). I found males had higher activity rates, and spent longer periods on spawning shoals, than females, in spite of similar daily travel distances between sexes. Overall, my findings challenge the conventional role of wind as a predominant predictor of lake trout spawning site quality. I propose that the unpredictable nature of wind and abundance of suitable habitat may favour lake-wide spawning by lake trout as a bet-hedging strategy in northern lakes with limited fetch. / May 2016

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

No description available.

Cette thèse a déterminé les rôles respectifs de la photopériode et de la température lors des différentes et successives étapes du cycle de reproduction (induction du cycle, vernalisation, ponte) chez la perche commune Perca fluviatilis femelle. La photopériode est le facteur environnemental principal qui synchronise l’induction du cycle de reproduction chez la perche commune, la température joue uniquement un rôle modulateur. Une baisse importante de la durée de la photophase de 4-8 heures est recommandée. Le maintien d'une photopériode constante basée sur une photophase longue et constante (17L : 7D) inhibe l’induction, alors que le maintien d’une température élevée et constante (22-23°C) ne le permet pas. Pour la phase de vernalisation, une photopériode de type jour court (8L : 16D) est nécessaire. Concernant les effets de la température, une forte et progressive baisse de la température (de 22 à 6°C sur 16 semaines) est recommandée pour assurer un développement gonadique complet (ovocytes aux stades de vitellogenèse avancée en fin de phase d’induction et de la maturation finale avant la période de ponte). Des baisses de température plus modérées (de 22 à 14-18°C) altèrent la reproduction, notamment pendant la phase de vernalisation. L’augmentation finale de la température après la vernalisation est le facteur principal de synchronisation de la ponte. Cette étude a permis la mise au point d’un protocole photo-thermopériodique fiable garantissant des taux d’induction et de ponte très élevés, proches de 100%, chez les femelles / This PhD thesis has determined the respective roles of photoperiod and temperature at the different and successive steps of the reproductive cycle (induction of the cycle, wintering period, spawning) in female Eurasian perch Perca fluviatilis. Photoperiod is the main environmental factor which synchronizes the onset of the reproduction cycle in Eurasian perch female, temperature plays only a modulating role. A high photoperiod decrease of 4 or 8 hours is recommended. The maintenance of constant photoperiod based on a long photophase (17L: 7D) delays the onset of the reproductive cycle, whereas the maintenance of a warm and constant temperature (22-23°C) does not delay it. For the wintering period, a photoperiod with a short daylight period (8L : 16D) is required. Concerning the effect of temperature variations, a high and progressive temperature decrease (from 22 to 6°C over 16 weeks) is recommended to ensure a complete ovarian development (all oocytes achieved the advanced vitellogenesis stage at the end of the induction phase and and final maturation stage just before spawning). Slight temperature decreases (from 22 to 14-18°C) alter the reproduction, especially during the chilling period (wintering period). The final increase of temperature (up to 14°C) after the wintering period is the main factor for spawning synchronization. This study allowed the development of a reliable photo-thermal protocol for out-of-season spawning with very high rates (close to 100%) of female response and spawning

Boshers dam vertical slot fishway, James River, Virginia, U.S.A., opened in 1999 and restored connectivity to 543.3 km of spawning habitat for anadromous fish. The fishway also allowed local movement of resident species. Video observation from 2001-2005 was used to evaluate environmental predictors of American shad (Alosa sapidissima) and sea lamprey (Petromyzon marinus) passage. The ecological effects of restoring connectivity to upstream habitat for gizzard shad (Dorosoma cepedianum) and blue catfish (Ictalurus furcatus) are also discussed. Regression analysis determined that the best predictor of increased daytime American shad passage is higher water temperatures and discharge and for increased daytime sea lamprey passage, a higher water temperature and increasing water temperature trend. Day length, and indirectly, barometric pressure also played a role in passage. Sea lamprey and American shad peak passage rates were dissimilar when comparing preferred water temperature ranges. Sea lamprey peaked (5.30/hr) at 16-17.99°C, while American shad peaked (1.05/hr) at 20-21.99°C. The diel pattern of passage for American shad indicated a strong diurnal tendency. All passage occurred during daytime hours, peaking from 1100 to 1900 hours. Diel patterns of sea lamprey indicated a strong nocturnal tendency (66% of passage occurring at night), with peak passage between 0300 and 0700 hours. More complete nightly passage data and passage data from periods when the water is too turbid for video observation would improve the accuracy of determining environmental predictors of passage.