One of the main environmental impacts of salmon aquaculture activities in the Bay of Fundy is the alteration of sediment chemistry as a result of the large amount of organic waste that accumulates below fish pens. To investigate these impacts, vertical profiles of delta13C, delta 15N, Corg, Corg:Ntot, FeHC1 , MnHCl, Ptot, PHCl, SO4 2-, AVS, Hgtot, and Hgpyrite in sediment cores collected throughout the bay were acquired. These profiles were then used to identify tracers of aquaculture activities and their impact on the redox zonation of the sediment. In addition, representative samples of fish food as well as farmed and wild salmon were analyzed to determine their Hg tot content as well as delta13C, delta15N, Corg, Corg:Ntot. / Our results show that, as by-products of salmon aquaculture (e.g., uneaten food, feces, antibiotics, and anti-fouling agents) accumulate in the sediments, their reactive organic carbon content increases and generate a greater oxygen demand. Subsequently, an upwards migration of the oxygen penetration depth and redox boundaries in the sediment column occurs, which is confirmed on the basis of the distribution of redoxsensitive phases (e.g., authigenic metal oxides and AVS) in the sediments. High resolution voltammetric microelectrode measurements show that the FeHCl and MnHCl distributions overestimate the oxygen penetration depth in the sediments. The total phosphorus distribution in the sediment record is shown to be a suitable tracer of marine aquaculture, reflecting the recent history of residual feed and fecal matter accumulation in the sediments. / Elevated mercury concentrations in sediments under fish pens are explained by its strong affinity for organic carbon. Although the source of additional Hg has yet to be resolved, as the organic carbon content of the sediments increases in response to the input from fish farming activities, so does the associated Hg. Mercury also partitions strongly to authigenic pyrite in the deeper sulfidic sediments. Of the few farmed Atlantic salmon analyzed, mercury levels were not elevated compared to the concentrations of mercury in the wild salmon captured in two rivers of the Canadian east coast.

Palmaria palmata and Chondrus crispus were cultured in the lab at three levels of temperature and two of nitrate, representative of commercial Atlantic halibut farming conditions. Productivity and nitrogen removal by P. palmata were greatest at temperatures <10°C. Productivity of C. crispus was greatest at >10°C, while nitrogen removal was unaffected by temperature, 6-17°C. When cultured in various nitrate and ammonium combinations, nitrogen uptake was highest when available as ammonium. Both species took up 89-100% of ammonium in 24 hours, but only 23-37% and 55-87% of nitrate was taken up by P. palmata and C. crispus, respectively. When P. palmata was integrated with halibut recirculating aquaculture, productivity and nutrient removal were compromised during summer. During winter, <11°C, nitrogen removal by P. palmata was relatively stable at 2.3 gN m-2 d-1. For 50% nitrogen removal from halibut aquaculture during winter, a finfish: seaweed biomass of 1: 1 would be required.

Red drum (Sciaenops ocellata) from seven of the nine major embayments of the Texas Gulf Coast were electrophoretically analysed for genetic variability. Indices of genetic similarity and distance were derived, as well as estimates of genetic divergence between bays. Cluster analysis phenograms were developed, and possible causes for population structure were addressed. Forty presumptive loci were screened, of which 30 proved to be of value for genetic population analysis. Percent polymorphic loci and heterozygosity/locus/individual ranged from 6.7%-13.3% and 0.025-0.042 respectively. These values were lower than those reported in similar studies, including some dealing specifically with Sciaenidae, but remained within the range reported for teleosts in general. A total of thirteen tests of genetic similarity/distance were performed. Of these tests, no segregation below a genetic identity of 0.95 was detected in those samples large enough to statistically satisfy the analysis. Upon exclusion of the small samples, no differentiation below 0.97 was demonstrated. Contingency chi-square tests and F-Statistics found only extremely low levels of divergence. Indeed, none of the divergence indicated was significant in terms of distinction of subpopulations among bays. This lack of differentiation in spite of apparently low levels of interbay migration was explained as a function of the dichotomus life stages. While juveniles are geographically isolated, adults occupy the open waters of the Gulf of Mexico, and have yet to be thoroughly described from either a life history or reproductive strategy viewpoint. The indicated single stock of reproductively active red drum in the Gulf requires further investigation, in order to accurately determine migrational habits as well as breeding success. The implications for management of the fishery at present are to regulate the resource as a single stock; as well as institute a comprehensive physical and biochemical study for future policy formulation.

This thesis investigates the comparative growth and mortality of a naturalized (wild) and domestic (aquaculture) strain of rainbow trout (Oncorhynchus mykiss) common to Lake Huron. I first conducted a laboratory-based experiment, comparing the growth rates of the two strains. Under optimal and competition treatments, the domestic strain achieved a body weight ~2x that of wild conspecifics. Next, I conducted a replicated, whole-ecosystem study comparing the same strains. Both strains experienced equally low survival and the domestic strain segregated into a fast-growing group, (~3x growth relative to the wild strain), and a slow-growing group that had a lower growth rate than wild trout. A high growth rate for fast-growing domestic trout was achieved by a reliance on high energy prey as well as through low metabolic costs relative to wild strains. Together, these results demonstrate that aquaculture strains of rainbow trout have greater growth potential relative to wild conspecifics and may outcompete them in nature.

Epilithic biofilms were monitored for potential impacts of an experimental rainbow trout aquaculture operation at the Experimental Lakes Area in northwestern Ontario, Canada. Metabolic and particulate samples were collected from the middle littoral zone of the experimental and reference lakes before and during the aquaculture operation. Phosphorus stocks in the experimental lake (epilimnetic and epilithic) increased as a result of both food waste and fish excretion. These cumulative P inputs were predicted to increase epilithic biomass and productivity, cause major compositional changes in the dominant groups and increase epilithic algal toxin production (microcystins). However, no major aquaculture-related changes in algal biomass, productivity, toxins or group dominance were observed in the epilithon. The only observed changes occurred at the species-level. These species-level changes were transient but did allude to an ecosystem reacting to stress.

The fate of farmed fish after escape is poorly understood. The extent to which these fish might impact freshwater ecosystems is dependent upon their survival and distribution in the wild. I simulated small- and large-scale escape events from two commercial aquaculture operations in Lake Huron over 2 years. I combined the use of telemetry (120) and Floy (1000) tags to determine the fate of escaped farmed rainbow trout (Oncorhynchus mykiss). Once released, escapees dispersed rapidly, showed low site fidelity (~15% after 3 months) and were capable of long distance movements (up to 360 km). Rainbow trout experienced low survival (~50%) but maintained high growth rates both at and away from the farms. The results of this study provide a strong basis for understanding the potential risks that farmed fish may pose to the Lake Huron fish community and ecosystem in an escape event.

No description available.

No description available.

<p> Environmentally-derived elemental and isotopic ratios in the otoliths of anadromous river herring (alewife, <i>Alosa pseudoharengus,</i> and blueback herring, <i>A. aestivalis</i>) were used to distinguish among groups of fish at spatial scales ranging from sub-populations within a watershed to populations from throughout the species' ranges. These ratios were also used to understand early life migrations and habitat use within and among populations. Sub-populations within the Hudson River, NY were accurately distinguished (> 95%), and populations from the Hudson River and Long Island, NY were distinct from each other and outgroups at varying distances, but accurate classification was dependent on the inclusion of oxygen isotopic ratios. Populations from Maine to Florida showed strong separation based on otolith signatures excluding (&sim; 70%) and including (> 90%) oxygen isotopes. Reclassification accuracies improved for both models by including genetic results in a hierarchical assignment model. Though all natural tags were effective for stock discrimination, the accuracy varied depending on the markers included; while inclusion of oxygen isotopes resulted in the highest reclassification rates, accurate application requires intensive sampling because of high interannual variability. Genetic markers reduce the effects of interannual variation because they are generally stable over generations. </p><p> Variations in otolith chemistry across an otolith (i.e. the fish's life history) can provide information about movements among habitats and especially along salinity gradients. Juvenile alewife within the Hudson River, NY (a large watershed) moved among multiple freshwater habitats, and trends varied widely among individuals while in the Peconic River, NY (a small, coastal watershed) three distinct movement patterns were observed. Retrospective analysis of Hudson River adult otoliths showed that multiple nursery habitats contribute to the spawning stock. Throughout the coast, retrospective analysis of adult otoliths showed that juveniles used fresh waters, estuaries, or a combination of both as nursery habitats and migratory behavior varied among populations, and were correlated to the latitude of the watershed, the watershed area, the amount of accessible river kilometers, and the percentage of the watershed in urban use.</p>

Epilithic biofilms were monitored for potential impacts of an experimental rainbow trout aquaculture operation at the Experimental Lakes Area in northwestern Ontario, Canada. Metabolic and particulate samples were collected from the middle littoral zone of the experimental and reference lakes before and during the aquaculture operation. Phosphorus stocks in the experimental lake (epilimnetic and epilithic) increased as a result of both food waste and fish excretion. These cumulative P inputs were predicted to increase epilithic biomass and productivity, cause major compositional changes in the dominant groups and increase epilithic algal toxin production (microcystins). However, no major aquaculture-related changes in algal biomass, productivity, toxins or group dominance were observed in the epilithon. The only observed changes occurred at the species-level. These species-level changes were transient but did allude to an ecosystem reacting to stress.