Reproductive characters of the elliptical star coral Dichocoenia stokesi (Cnidaria: Scleractinia) were investigated based in histological examination of tissues collected in southeastern Florida between September 1999 and September 2000. The study population was predominantly gonochoric with a small incidence of hermaphroditism. Dichocoenia stokesi exhibits intermediate egg size (312.2 ± 40.4μm; mean ± SD) compared with other scleractinian species, suggesting a moderately lecithotrophic larval stage. Although spawning was not directly observed in this study, two separate spawning events per year are inferred from histological slide analyses; the first in late August or early September, and the second in early October. Sea water temperature was significantly positively correlated with female gonadal development in D. stokesi, whereas insolation was significantly inversely correlated with gonadal development. A recent epizootic of White Plague Type II in south Florida appears to be skewing local D. stokesi populations toward smaller - and potentially less fecund - colony sizes, although colony size and fecundity were not correlated in this study. The mean fecundity of the study population is estimated as 1138.1 eggs cm-2 yr-1.

The stone crab, Menippe mercenaria, supported the third most valuable fishery in Florida in 2016. Declining catch per unit effort (CPUE) and overall negative trend in landings since 2000 have raised concerns among fisherman, researchers, and fishery managers about the resiliency of the fishery. The Florida Fish and Wildlife Research Institute estimated that the Florida stone crab fishery has been overexploited since 1997. Overexploited fisheries, such as the commercial stone crab fishery, risk induced changes in life history parameters, such as age at maturation and reproductive output. In turn, these population-level changes have the potential to reduce the spawning stock biomass and future recruitment to the fishery. The research presented in this dissertation was intended to assess the Florida stone crab fishery stock for: 1) size at sexual maturation in females, 2) size at maturation in males, 3) potential fecundity, modeled as a function of spatial and temporal variables, 4) spawning potential ratios, an index that reveals potential recruitment overfishing, by formulating a per recruit model using the reproductive indices developed in this research, and 5) evaluating the impact of management changes on the spawning stock biomass. The physiological, behavioral, morphological, and functional maturity of female stone crabs were assessed in individuals collected throughout the fished range of the population on the west Florida shelf (Cedar Key – Sawyer Key). Histology was used to determine oocyte maturity, presence of spermatophores, and presence of postovulatory follicles. Decision-tree analysis suggested that 50% of female stone crabs were mature at 43 mm carapace width, when using a combined variable of physiological and behavioral maturity. The decision tree accurately classified 98% of mature females and 85% of immature females. Morphological maturity was assessed using piecewise regression to determine where allometric changes in growth occurred between carapace width and crusher claw length. The transition point between mature and immature females occurred at a carapace width of 66.3 mm. Differences in estimates of size at sexual maturity between morphological and physiological, behavioral, and functional maturity indicate that relative growth of body parts is not a reliable estimate of sexual maturity in stone crabs. Histological analysis revealed that smaller females are contributing to the spawning population more than previously estimated. The corresponding carapace width at which female stone crab claws are vulnerable to harvest, occurs at 78 mm. The new estimates indicated that females contribute to the spawning population 1-2 times prior to vulnerability to the fishery. Continued monitoring of sexual maturity using these methods is recommended to strengthen understanding of the fishery and of interactions between stone crab populations. Two methods were used to assess sexual maturity physiologically and morphologically in male stone crabs collected throughout the range of the fishable population. Histology was used to identify the production of spermatophores in the anterior vas deferens, indicating physiological maturity, and each crab was assigned a maturity stage. Decision-tree analysis suggested that physiological maturity occurred at a carapace width of 34.8 mm, accurately classifying 98.9% of mature males accurately and 72.5% of immature males. Piecewise regression estimated that the allometric relationship between carapace width and crusher claw length changed at a carapace width of 63.1 mm. The difference between physiological and morphological estimates of size at sexual maturity indicates that, like females, changes in male allometric relationships between body parts may not be a reliable indicator of sexual maturity. Large morphometrically mature males may be more successful in mating encounters, but in times of flux in population size structure, morphologically immature, but physiologically mature, males may have more opportunities for successful mating encounters. Carapace width at which male stone crab claws are vulnerable to the fishery occurs at 88 mm, indicating that they are capable of contributing to the reproductive population multiple times prior to vulnerability to the fishery. Multiple factors influencing variability in stone crab batch fecundity were quantified across Florida fishery sites, by implementing a negative binomial model. Fecundity was strongly and positively related to carapace width, and parameter estimates indicated that batch fecundity was on average higher at Pavilion Key (southwest Florida) and Tampa Bay (central Florida), relative to Sawyer Key (south Florida) and Cedar Key (northwest Florida) sites at the northern and southern ends of the study area. Fecundity varied among 2013-2016 and was highly variable among months. In general, the lowest batch fecundity occurred in winter and spring months, while peak batch fecundity occurred in July and August, highlighting the common seasonal trend in crustacean reproductive cycles. Comparison to a 1993-1995 study of fecundity estimates in Tampa Bay, Florida indicated that there was little change in stone crab fecundity between individuals collected in 1993 and 2013. However, this temporal relationship accounts for a small portion of the fished population and may not be reflective of the changes over time across the entire fishery. Although sea surface temperature and ocean color data do not explain the variability in fecundity between sites, I hypothesize that food quality and quantity and fishing effort may play critical role in regionally variable individual reproductive output. I suggest that given the variability in reproductive output and regional fishing practices, that further work be dedicated to identifying critical spawning and recruitment areas to ensure resiliency of the stone crab population. Spawning potential ratios were used to evaluate the impact of alternative biological and management scenarios to the reproductive output in a theoretical stone crab population. The model incorporated the findings of size at maturation and fecundity established in previous chapters, as well as contemporary temperature-dependent declaw mortalities. Spawning potential ratios increased with decreasing size at sexual maturity and were sensitive to past and present estimates of size at sexual maturity, and increasing natural mortality. However, the largest contributor to changes in the fished stock appears to be mortality associated with declawing and releasing stone crabs. We assessed various management scenarios including declaw lengths, vulnerability to capture, and variable season timing and length. Increases in declaw length and size at vulnerability to capture provided moderate protection to the spawning stock. The model estimated that adaptive management regulations which considered the timing and duration of seasonal fishing, based on mean monthly temperatures below 24°C (temperature at which declaw mortality increases), had the potential to greatly reduce mortality, and provided protection to the spawning population. The model was able to examine a wide range of biological and management scenarios; however, more research should be conducted to determine the socioeconomic impact of regulation changes. The Florida stone crab fishery is an amalgamation of unique fishing practices, rich culture, and both regional and economic influence. Evolving fishing practices, conservation initiatives, and environmental conditions have the potential to transform the fishery. Therefore, fisheries managers, scientists, and stakeholders must work cooperatively to ensure the resiliency of the stone crab fishery.

A critical step in ecological speciation is the development of reproductive isolation. The processes leading up to reproductive isolation are difficult to study since they often occur over very long time periods. Populations of European whitefish (Coregonus lavaretus) has gone through reticulate divergent evolution in many Scandinavian lakes during the last 10 000 years. Some populations even exhibit morphological and genetic divergence that involves adaptations to different niches during the first 100-200 years after introduction. This observed rapid diversification into different ecological niches makes whitefish a useful model species for studying ecological speciation and early population divergence. By assessing divergence for three traits in recently introduced whitefish populations, this study aims to elucidate the processes that lead to adaptive phenotypic divergence and reproductive isolation. Whitefish populations of known age (71-170 years) were sampled on their spawning grounds and characterized with respect to, 1) length of spawning season, 2) temporal segregation based on body size, and 3) temporal segregation based on the number of gill rakers. I found that the length of the spawning season and body size differences between early and late spawners increased with population age. No such trend was observed for differences in gill rakers between early and late spawners, but significant divergence within some of the older populations was detected. I conclude that these young whitefish populations have taken the first steps toward reproductive isolation between ecotypes that differs in body size (a highly plastic trait) and gill raker numbers (a trait under strong genetic control).

The source of a reliable supply of seed is one of the most important factors determining the success of aquaculture. At present mud crab culture is reliant on wild caught juveniles, which limits the expansion of mud crab farming globally. This, coupled with the paucity of knowledge of the spawning and egg characteristics of mud crabs, prompted the investigation into the captive spawning, incubation and egg quality of Scylla serrata in South Africa. A total of 112 mature females were caught from three estuaries in northern KwaZulu Natal and acclimated to captive conditions. Mature females were present in the estuaries throughout the year and ranged from 90 to 200 mm carapace width. Except for 40 crabs all the females spawned in captivity. On average spawning took place 38 ± 23 days after capture but was not dependent on crab size. Fecundity was significantly correlated to crab size (p = 0.026), with larger females producing more eggs. The average fecundity per batch was 5.79 ± 2.07 million eggs. Hatch success rate for all egg batches was high averaging 84 ± 6 %. Egg dropping occurred in all egg batches during incubation. On average 6.5 % of the egg mass was dropped during incubation. At the average temperature of 27⁰C eggs in the incubation system hatched within 292 ± 12 hours after extrusion. In-vitro incubation of eggs proved to be an ineffective means of incubating Scylla serrata eggs with a hatch success rate of only 25 ± 5 %. Egg quality was assessed both directly, using variables such as hatch success rate and hatch synchronicity and retrospectively by using stress tests and comparing survival of larvae from different coloured egg batches. Lipid class composition and fatty acid methyl ester content for 28 batches of eggs and 16 batches of larvae were analyzed. The biochemical composition of the egg was correlated to survival of larvae in the stress tests to ascertain if the lipid content of the eggs determines their quality. Stress tests were used to retrospectively assess egg quality. Four stressors were administered to newly hatched larvae and the LD50 values recorded. An average LD50 of 64 hours was recorded for the starvation tests, 40% for the salinity tests, 37 ppm for the formalin tests and 39.7 mg/l NH3 for the ammonia stress tests was recorded. Egg colour ranged from pale yellow to orange-red. Egg colour was not influenced by female size or the time the females spent in captivity prior to spawning. Egg colour can therefore not be used as an indicator of quality. The lipid profiles of newly extruded eggs had no effect on hatch synchronicity or hatch success rate. However, the stress tests identified female size (p ≤ 0.02), DHA content of the egg (p ≤ 0.02), Σ omega-3 fatty acids of eggs (p ≤ 0.02) and EPA content of eggs (p ≤ 0.007) as possible determinants of egg quality. Larger crabs tended to produce poorer quality eggs. Egg quality also decreased as the amount of DHA, EPA and the Σ omega-3 fatty acids decreased in the eggs. To summarize, the results of this study indicated that the following parameters affect egg quality - crab size, DHA, EPA and Σ omega-3 fatty acid content of eggs.

Erratic and highly variable catches in the South African chokka squid Loligo vulgaris reynaudii fishery, cause socio-economic hardship for the industry and uncertainty for resource managers. Catch forecasting can reduce this problem as it is believed that catch variability is strongly influenced by environmental factors. In this study, data were collected at varying temporal and spatial scales. Data for the hourly time-scale study were collected from 1996-1998, aboard commercial vessels, whilst for the longer time-scales, data were extracted for Kromme Bay (a single fishing area) from existing databases (1991-1998) that were comprised of compulsory catch returns and oceanographic data. The environment-catch relationship for chokka squid on the inshore spawning grounds was then investigated using multiple correlation and regression analysis, analysis of variance, contingency table analysis and cross-correlation statistical techniques. This simple, direct, 'black box' statistical approach was relatively successful in developing a predictive capability. On a short time-scale (hourly), the regression model accounted for 32% of the variability in catch, with turbidity the main determinant (13%). On a daily monthly time-scale, the best prediction model was on a monthly scale, accounting for 40% of the variability in catch. The principal determinant, bottom temperature anomaly (11 %), was found to lag one month forward. Seasonal and diel catch variations induced changes in the relative importance of turbidity, water temperature and wind direction on catches. A strong, positive relationship was found between easterly winds (which cause upwelling) and catch, particularly in summer. Catch rates, however, decreased with an increase in turbidity. The correlation between temperature and catch was generally negative, however, higher catches were associated with a temperature range of 13-18°C. Highest catch rates were associated with easterly winds, zero turbidity conditions and sea surface temperatures from 15.0-16.9°C. Selected case studies (in situ observations) suggested that upwelling and turbidity events act as environmental triggers for the initiation or termination of the spawning process, respectively. A holistic approach is required to improve predictive capability of chokka squid abundance. Although short-term predictability remains essential (i.e. hourly-scale), future research should concentrate on long-term prediction models (e.g., monthly time-scales) involving greater spatial variation, which are the most important for management.

Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye. / Forestry, Faculty of / Graduate

The success of the larval stage in fishes plays a critical role in structuring adult fish populations. It is well understood that juveniles of many marine fish species are closely associated with nearshore and coastal habitats that serve as nursery areas while adult assemblages are more widely distributed. The larval phase however, particularly pertaining to nursery habitat use, remains poorly understood in South Africa. A mixed-method, larval and juvenile fish study was conducted in the warm-temperate shallow coastal waters of Algoa Bay, South Africa. Two years (2010 – 2012) of seasonal sampling at 27 stations at various habitat types revealed distinct spatio-temporal patterns in larval fish composition and abundance. In total, 164 species from 50 families were collected in the nearshore (<30 m), over reef and sand, in the surf zone and large estuarine habitats in Algoa Bay. Engraulidae dominated the larval fish catch in the nearshore (38.4 percent) and over the selected reef and sand habitats (37.8 percent). Cynoglossidae (28.1 percent) and Sparidae (8.4 percent) were the second and third most abundant fish families in the nearshore. In subtidal reef and sand habitats, Gobiidae (23.4 percent) and Clupeidae (9.2 percent) were the second and third most abundant families respectively. Sparidae dominated (71.4 percent) surf zones followed by Soleidae (10.8 percent) and Mugilidae (5.3 percent), while in the mouth area of two permanently open estuaries in Algoa Bay, Gobiidae (35.9 percent) Sparidae (30.1 percent) and Mugilidae (12.4 percent) dominated. Several species from the Blenniidae, Gobiesocidae, Gobiidae, Scorpaenidae and Tripterygiidae fish families complete their pelagic larval phase in the reef habitats in Algoa Bay. These reef habitats therefore serve as important nursery areas for the larvae of benthic species. The sand and nearshore habitats serve as nursery areas for Clupeidae and Engraulidae. Highest densities of Carangidae, Sciaenidae and Sparidae larvae were observed at the subtidal reef habitats indicating that this area is important for accumulation of the early developmental stages of these fishes. The nearshore serves as an important accumulation habitat for species in the Haemulidae and Soleidae families whose juveniles are known to recruit into estuarine nursery areas. The nearshore therefore is a specific area of presettlement buildup of larvae prior to settlement of larvae or juveniles in estuarine nursery areas. Cynoglossidae larvae are also using the nearshore as an accumulation area prior to settlement and recruitment into adult populations occurring in shallow water habitats. In the surf zone, not only are estuary-dependent fish species utilizing this habitat as a nursery area, but marinespecies whose adults are either associated with rocky shores or surf zones are similarly using these areas as nursery habitats. In addition, estuary-dependent fish species which spawn in the marine environment are actively recruiting into estuarine nursery areas on both tides. Active recruitment against the outgoing ebb tide flow was a conclusive finding in this study. These larvae and juveniles are actively swimming against the ebb tide in the shallower, slower-flowing marginal areas where current flow is reduced. Strong environmental gradients on multiple temporal and spatial scales occur in Algoa Bay. Seasonal patterns were evident in larval densities, richness and diversity. Peaks in density, richness and diversity occurred during spring and summer (September to February) associated with increasing water temperatures and a high productivity providing a good food environment for larval fishes. Thereafter densities declined steadily as a result of natural mortality, settlement or adult spawning activity, until autumn when numbers dropped suddenly as the surviving larvae moved to settlement habitats. The relationship between larval fish and environmental variables provides information useful to determine distributions. Therefore the Bay is particularly suited for modelling larval fish distributions. Using generalized linear models, larval fish density in the nearshore of Algoa Bay responded to different ocean features to varying degrees. Larval fish density responded positively to both upwelling and when warm water plumes, originating from an Agulhas Current meander, entered Algoa Bay. On subtidal reefs, habitat complexity played an important role in determining larval fish composition and diversity. The less structurally complex, reefassociated sand habitats, yielded higher species richness and diversity than the high and low profile reef habitats. Therefore, it is likely that the importance of less structurally complex habitats has been overlooked relative to other habitats in terms of their function for larval fishes. In the surf zone, wave period and wave height, which can be related to exposure, were the most significant environmental factors influencing larval fish assemblages. Greatest species diversity was observed in the surf zone habitats heavily influenced by wave action in the windward sector of Algoa Bay. The identification of spawning areas and the mapping of distributions of early developmental stages of fishes are important in providing data pertaining to the protection of these habitats. This is particularly relevant as a new marine protected area MPA)is planned for the eastern sector of Algoa Bay. Results from retrogressive plots indicate that the spawning locations of several species of coastal and pelagic fishes are occurring outside of the Bay, with the bay therefore serving as an accumulation area. Furthermore, distribution modelling results demonstrate that the early developmental stages of fishes in the shallow coastal habitats of Algoa Bay exhibit high spatial variability in their distributions. Results presented in this thesis help fill the knowledge gaps critical to the understanding of larval fish nursery areas of several economically and ecologically important fish species in Algoa Bay.

Recordings of fish sound production were made in Charlotte Harbor, Florida using Long Term Acoustic Recording Systems (LARS) programmed to record 10 seconds of sound every 10 minutes. Results demonstrated a strong circadian pattern in fish sound production that occurred within a few hours of dusk each evening. Sound production lasted on average 8.7 hrs each evening during the peak spawning season. LARS were deployed when Hurricane Charley crossed Charlotte Harbor in August, 2004. The hurricane did not inhibit nightly chorusing events of spawning fish. Rather, sound levels produced by spawning fish on the night of and 3 days after the hurricane were higher and lasted longer than any of the 9 days recorded prior to the hurricane. Acoustic time series data recorded at multiple sites in Charlotte Harbor during 2005 revealed changes in the spatial distribution of fish sound production in response to increased freshwater inflow and consequent decreased bottom dissolved oxygen concentrations in early June. Fish sound production decreased rapidly over several days at study sites in the northern portion of the harbor most immediately affected by changes in environmental conditions. Meanwhile, fish sound production increased at the study site furthest seaward where normoxic levels were sustained. By August levels of fresh water inflow decreased substantially, bottom dissolved oxygen levels increased and sound production resumed at sites previously affected by these conditions. Fish sound production began intermittently in February and ended in November. Peak levels were reached by mid-late April / early May and continued throughout the summer time. Seasonal patterns of sound production match the reported spawning periods of estuarine sciaenid species recorded. Black drum sound production was measured in the canal systems of Cape Coral and Punta Gorda, Florida during the 2004-2006 spawning seasons. The circadian pattern of sound production was similar to other sciaenids documented in Charlotte Harbor. Seasonal patterns of black drum sound production occurred during October through April and peaked in February. This seasonal period of sound production also matched patterns of black drum reproductive readiness and spawning reported in the literature for the Gulf of Mexico. A hydrophone array was used in the Cape Coral canal system to localize calling black drum and measure source levels and propagation of calls. Source level estimates averaged 165 dBRMS re: 1muPa SPL (SD=1.0) (n = 1,025). Call energy was concentrated in the fundamental frequency (94 Hz) and first two harmonics (188 Hz and 282 Hz). A square root model best described propagation of the fundamental frequency and first harmonic and a log 10 model best described the second harmonic. Based on the mean RMS source level, signal propagation, background levels, and hearing sensitivity, the communication range of black drum at the study site was estimated at between 33 and 108 meters and was limited by background levels, not auditory sensitivity. The timing and levels of sound production and egg production were compared in black drum. Eggs were collected hourly from 1800 - 0400 by surface plankton tows on two consecutive evenings while black drum sound production was continuously recorded. This sampling effort was conducted five separate times from January through April, 2006. Evidence of the time of spawning was indicated by the collection of blastodiscs (fertilized single cell eggs) or back calculated early cleavage stage eggs. Neither the timing nor the quantity of sound production was positively correlated with egg production on a nightly basis and the greatest densities of eggs were collected on evenings which had the lowest levels of sound production. This may have been due to differences in the fecundity of individual females spawning on the evenings when sampling was conducted.

I described the spawning ecology of the Bear Lake Bonneville cutthroat trout (BLBCT) in St. Charles Creek. I tracked cutthroat trout with used radio telemetry. I conducted redd counts to describe spawning conditions. Most cutthroat trout in the Big Arm strayed into the Bear River. Cutthroat trout migrations in the Little Arm and main fork were very limited (<4 km). Redd distributions showed very similar patterns between 1989, 2000 and 2001 with most redds being built in the lowest kilometer of stream. Artificial fish transportation changed the redd distribution in 2002. More redds were built in the main fork and redds were distributed throughout the stream. Redds built in the main fork were characterized by lower levels of fine sediment and higher water velocities as compared to the redds built on the Little Arm. The results of this research will be used to aid resource managers in developing a management plan for wild BLBCT.

The federally endangered June sucker (Chasmistes liorus mictus), which is endemic to Utah Lake, UT, historically spawned in all significant tributaries flowing into Utah Lake. However, due to a variety of anthropogenic changes, June sucker spawning is now primarily restricted to the Provo River, the largest tributary to Utah Lake. The purpose of this study was to gain a better understanding of the spawning and early life history of the June sucker. My specific objectives were to determine (1) what environmental factors attract or deter June suckers to certain Utah Lake tributaries for spawning; (2) what cues June suckers to migrate upstream to spawn; (3) if June suckers use more than one tributary for spawning; and (4) what limiting factors exist in these smaller tributaries. I performed weekly trap-netting surveys and installed passive integrated transponder tag interrogation systems into five Utah Lake tributaries during the spring of 2008 to determine if suckers were using multiple tributaries for spawning and to determine the timing and number of fish migrating upstream to spawn. I coupled the trap-netting data (staging) and migration data (tributary use) with a suite of biotic and abiotic environmental variables in a random forest model to establish the strongest relationships that exist between fish migration and environmental factors. I found that June sucker were present at the mouths of all tributaries sampled and migrated up three of the five tributaries during the spawning season. The Provo River was the tributary most used. Evidence of reproduction was found in four of the five tributaries by the presence of larval June sucker. The random forest model, for staging, indicated that lower total dissolved solids of the tributaries influenced higher catch per unit effort at the mouths of the tributaries, but explained only 33% of the variance. The random forest model, for tributary use, performed very well, explaining 85% of the variance and indicated discharge was the most important variable for upstream migration. Specifically, the ascending limb of the hydrograph appeared to cue migration and the descending limb cue spawning. I also found the most likely limiting factors in the smaller tributaries are degraded water quality and available spawning habitat. Results from this study show fish are selecting less degraded streams for spawning. Stream restoration projects, in the smaller tributaries, would likely increase the spawning habitat for June suckers and aid their recovery.