Over the past two centuries, anadromous alewife populations have drastically declined due to damming, inadequate fish passage, overfishing in the ocean and freshwater, climate change, and reduction in habitat quality. Alewife populations are currently assessed by counting adult fish as they migrate upstream, but little is known about resulting juvenile production within lakes. Lack of knowledge of freshwater life history characteristics of juvenile alewife limits our understanding of overall productivity. For this thesis, I fill existing information gaps by (1) characterizing the timing of adult alewife migrations and subsequent spawning (Chapter 2), and (2) assessing juvenile alewife density, size, growth, and mortality within lakes, and abiotic factors influencing these estimates across lakes (Chapter 3). Twenty lakes across coastal Massachusetts were sampled for juvenile alewife and water quality in summer 2014. Each lake was sampled three times: Round 1 (29 May to 15 June), Round 2 (26 June to 16 July), and Round 3 (27 July to 15 August). Analyses of instream adult counts and otolith-based estimates of spawning date from captured juveniles showed a distinct delay (7-28 d) between the beginning of the adult migration run and spawning, and spawning continued 13-48 days after adults stopped migrating. These findings further corroborate recent discoveries that suggest alewife exhibit asynchronous spawning and has large implications for freshwater foodwebs. Lakes, overall, did not produce the same sized fish and there appears to be substantial variations of length-at-age with some lakes exhibiting large differences. No change in length-at-age occurred in August, thus differences were achieved earlier in the growing season. Additionally, all 20 lakes exhibited variable growth, density, and mortality rates that yielded generally weak relationships with abiotic and biotic factors. Juvenile alewife density was positively related to juvenile density in the previous sampling Round, suggesting that a single sampling date may be sufficient to estimate relative lake density across the landscape. Factors affecting growth were not consistent; overall growth was positively correlated with DOC, while the last 20 days of growth was negatively correlated with secchi depth. While different, these responses are likely the result of the same mechanisms, both intrinsically linked with zooplankton abundance, prey availability, and feeding behavior within lakes. No significant correlate was found for mortality. In the future, the data in this thesis can be incorporated into models to improve stock assessments and support timely adaptive management strategies.

<p dir="ltr">Blanding’s turtles (<i>Emydoidea blandingii</i>) and Wood Turtles (<i>Glyptemys insculpta</i>) are two threatened species that face various natural and anthropogenic threats to their populations. Many of these threats cause a decline in their recruitment, which can lead to drastic declines in populations. Females put themselves at-risk during periods of movement. My objectives were to identify portions of the season that females were most at-risk, potential nest predators, preferrable nest microhabitat characteristics, and movement of hatchlings. I studied movements in adult females of both species at a site in Northern Michigan using GPS and radiotelemetry. I compared these movements to the relative level of risk, or resistance, in the path they chose to take. I found both species had relatively similar resistance movements over the entire season. It seems that Blanding’s turtles tend to make more resistant movements during nesting, while Wood Turtles seem to be less resistant. Neither species seems to take the least resistance path available. I also conducted nesting surveys to determine nesting locations and selection characteristics at the site for both species. I did not find any characteristic that predicts nesting locations. The located nests were also recorded via trail cams to assess for predator activity. I recorded many species on trail camera review, but I did not note any predation behavior, all damage to nest cages were caused by humans and their vehicles. Lastly, I used radiotelemetry to analyze movements for hatchling turtles. Hatchlings of both species tended to make short daily movements until they reached a wetland. I also found hatchling’s succumbed to predation, desiccation, and road mortality. My data suggests further research needs to be conducted to expand our knowledge on recruitment threats. Nevertheless, I suggest active management for the threats we have noted. Nest cages seemed to be relatively successful at protecting nests, so I recommend continued nest cages to prevent or deter predators. Head-starting may be a strong strategy to help hatchlings reach a larger size before release. These larger hatchlings would also allow for larger transmitters and longer tracking times. This will help to prevent lost turtles and further our knowledge on hatchling success.</p>

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No description available.

Benthic macroinvertebrates and physicochemical parameters were sampled monthly in Spring Lake, Florida from July, 1978, to June, 1979. Spring Lake is a slightly acidic, sand bottom lake located in the sandhill region of the Central Highlands. While submersed vegetation is not dense, the lake does contain an abundance of the endemic submersed plant Mayaca aubletii. The littoral zone is dominated by plants belonging to the genera Panicum, Nuphar, Hydrocotyle, Nymphaea, Satittaria, and Typha. The benthic macroinvertebrates collected consisted of 51 species; approximately 50 percent were in the family Chironomidae. The annual mean number of individuals was 947/m2. The mayfly Hexagenia munda Orlando was the most numerous species (18.4 percent of the annual mean); the Chironomidae was the most numerous family (31.6 percent of the annual mean). The annual mean value for the Simpson's Index was 0.25 while the annual mean value for the Shannon Index was 2.60.

Benthic macroinvertebrates and physicochemical parameters were monitored simultaneously with hydrilla in a central Florida lake. Changes in the benthos were described in relation to plant growth. Twenty-seven of the 54 taxa of benthic macroinvertebrates collected were members of the Family Chironomidae. Chironomids and oligochaetes numerically dominated the benthos, comprising of 82% of the individual collected. The greatest numbers of species and individuals were found during the winter when hydrilla biomass was low. Hydrilla biomass ranged from 0.385 kg/m2 in April, 1977 to 2.275 kg/m2 in October, 1977. Low numbers of species and individuals were collected from bottom sediments during summer and fall. Dissolved oxygen concentrations at the bottom were approximately 2.0 ppm during summer and fall and possibly limited benthic organisms. The annual means for the Shannon and Simpson Indices for the benthos were 1.92 and 0.36, respectively.

There is no single methodology toward freshwater conservation planning, and few analytical tools exist for summarizing ecological risks at a landscape scale. I constructed a relative risk model, the Ecological Risk Index (ERI), to combine the frequency and severity of human-induced stressors with mappable land and water use data to evaluate impacts to five major biotic drivers: energy sources, physical habitat, flow regime, water quality, and biotic interactions. It assigns 3 final risk rankings based on a user-specified spatial grain. In a case study of the 5 major drainages within the upper Tennessee River basin (UTRB), U.S.A, differences in risk patterns among drainages reflected dominant land uses, such as mining and agriculture. A principal components analysis showed that localized, moderately severe threats accounted for most of the threat composition differences among watersheds. Also, the relative importance of threats is sensitive to the spatial grain of the analysis. An evaluation of the ERI procedures showed that the protocol is sensitive to how extent and severity of risk are defined, and threat frequency-class criteria strongly influenced final risk rankings. Multivariate analysis tested for model robustness and assessed the influence of expert judgment by comparing my original approach to a quantile-based approach. Results suggest that experts were less likely to assign catchments to high-risk categories than was the quantile approach, and that 3 final risk rankings were appropriate. I evaluated the influence of land use on freshwater ecosystems by studying the relationship between land cover changes and the persistence of freshwater mussels. First, historical species data were collected and the Upper Tennessee River Mussel Database (UTRMD) was constructed. The UTRMD contains >47,400 species records from 1963-2008 distributed across nearly 2,100 sampling sites. My study suggests that 30 years of land cover change does not explain observed freshwater mussel declines. Quantitative surveys are recommended basin-wide to provide more accurate information about mussel distribution and abundance. Lastly, results suggest that streams with repeated mussel surveys have increasing populations, including active recruitment in several beds. Additional quantitative surveys since 2004 have probably provided more accurate species and population counts, although actual population sizes are still uncertain. / Ph. D.

Analysis of trophic and population ecology of an introduced (1968- 1969) alewife forage base and resident sportfishes (age 0 and older) indicated several negative trophic interactions within the community complex of Claytor Lake, Virginia. Alewife piscivority represents a potentially significant adverse impact on sportfish recruitment. Alewife consumed the young of at least four sport species. Larval alewife did not inhabit shallow coves and consequently were not a prey item of age 0 sportfish resident in that habitat. Dietary overlaps (Levins' equation) between adult alewife and young-of-year sportfishes indicated that competitive interactions may occur on a time/site-specific basis. Alewife were demonstrated to be highly size-selective planktivores, preferring zooplankters >1.0 mm length. Electivity determinations indicated the importance of considering size distribution of prey species in food-habit studies. Electivity values were often positive for zooplankters ≥1.0 mm and negative for those <1.0 mm length. Comparisons of the zooplankton community following an alewife die-off (1978) and after alewife recovery (1979) indicated that changes in abundance of predominate species were size-related with smaller forms dominating after alewife recovery. The sizes of Daphnia at onset of maturity were considerably smaller following alewife population recovery. Alewife-induced shifts in zooplankton composition toward small forms represent a potentially significant adverse impact on young-of-year sportfishes which are often size-dependent as well as size-selective planktivores. Electivity determinations of young-of-year sportfishes (<50 mm TL) indicated that only striped and white bass positively selected a zooplankton species (Leptodora kindtii) that was concurrently preferred by alewife. Partitioning of the food complex among cove-inhabiting young sportfishes was in evidence. Predation upon one another, as well as cannibalism appeared to be a more critical trophic interaction than competition with each other or alewife. Indirect trophic interactions between alewife and planktivorous sportfish stages may have affected first year growth rates of smallmouth bass, spotted bass, and white crappie which declined compared to results of a previous growth study made prior to alewife introduction. Following the alewife die-off, age 1 white bass and walleye growth rates significantly increased, perhaps in response to reduced competition with alewife. Utilization of alewife (age 0 and age 1 only) by pelagic sportfishes (walleye, striped bass, white bass) and predation of other prey by littoral black basses suggested partitioning of the forage base. In the spring following the alewife die-off, pelagic sportfishes switched to alternative prey and competition among limnetic and littoral-inhabiting piscivores presumably increased. Although alewife were shown to possess several negative traits for a forage fish, no forage species has proven ideal for southeastern reservoirs. Alewife introduction should be limited to systems too cold for threadfin shad, and that are managed primarily for pelagic predators with non-pelagic young or those that are maintained on a put-grow-take basis. Results of this study underscore the importance of assessing community impacts of an exotic species before wide-spread introduction. / Ph. D.

Study of two sections of a stream associated with highways of different traffic densities and a third section used as a reference area demonstrated that concentrations of lead, nickel, cadmium, and zinc in sediments, benthic macroinvertebrates, and fish were highly correlated to the amount of traffic associated with the respective sampling site. Highest sediment concentrations of lead, nickel, and zinc occurred in spring, most likely due to accumulation and subsequent runoff in snow. Accumulation of these metals in invertebrates and fish is probably a more· time-dependent process. Concentrations in these organisms were related to physiological and ecological factors as well as the relative availability of each metal at each study site. The major physiological factor influencing accumulation of heavy metals in stream organisms seemed to be the relative amount of tissue with a high affinity for these metals in each organism. The major ecological factor influencing accumulation of heavy metals seemed to be the relative amount of sediment association characteristic of each species. Invertebrates contained the highest levels of each metal, followed by bottom-oriented fish with a small proportion of muscle, while species of fish with a large percentage of muscle inhabiting the upper water column contained the lowest concentrations. Biomagnification of these four metals was not demonstrated. Significant bioaccumulation of lead, nickel, and cadmium in bone; and cadmium in the kidneys of fish was found to occur. Major biological uptake of lead, nickel, cadmium, and zinc in these organisms was via water and/ or sediment-water interaction. / Master of Science