Members of the family Platytroctidae (tubeshoulders) are found throughout the meso- and bathypelagic waters of the World Ocean. Due to the lack of specimens collected globally, this taxon has received little attention, despite recent evidence suggesting its predominance in the bathypelagic biome. Prior to this study, only four species had been reported in the Gulf of Mexico’s (GoM) highly diverse deep-pelagic ecosystem. An extensive meso- and bathypelagic trawl series in the GoM allowed a detailed examination of this family, which included analyses of species composition, abundance, vertical distribution, sex ratios, and trophic ecology. A total of 16 species were collected, which included 12 new records for the GoM. The five most-abundant species collected were Mentodus facilis, Platytroctes apus, Barbantus curvifrons, Mentodus mesalirus, and Maulisia microlepis. All platytroctids were collected from tows that extended below 700 m. Mentodus facilis was the only species that significantly differed from the expected 1:1 sex ratio (pMentodus mesalirus and Maulisia microlepis heavily consumed gelatinous zooplankton. Mentodus facilis and Barbantus curvifrons had a more varied diet consuming chaetognaths, copepods, and ostracods, with M. facilis exhibiting a slightly greater reliance on ostracods and gelatinous prey. This study represents the first investigation into the diet of this fish family and adds to the sparse community data of the bathypelagic zone by identifying alternative nutrient pathways (e.g., the fish-jelly link) that connect the deep and upper oceanic ecosystems.

Zooplankton samples were collected from 166 Oregon lakes. The lakes included a wide range in size, trophic status, and water quality. Lakes were located throughout the state. Zooplankton were identified using standard taxonomic keys and counted. Seventy-four species were identified from the 200 total samples, including 32 species of cladocera, 22 copepods, and 11 rotifers. Two species of copepod were recorded for the first time in Oregon: Diaptomus mississippiensis and Diaptomus pallidus. Seven species had widespread distributions throughout most of the watersheds in the state. Seventeen other species had distributions restricted to eastern, central, or western Oregon. The remaining species were either rare or had random distributions.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 297-213). / This thesis explores the role that the circulation in the Gulf of Maine (GOM) plays in determining the distribution of dense aggregations of copepods. These aggregations are an important part of the marine ecosystem, especially for endangered North Atlantic right whales. Certain ocean processes may generate dense copepod aggregations, while others may destroy them; this thesis looks at how different characteristics of the GOM circulation fit into these two categories. The first part of the thesis investigates a hypothetical aggregation mechanism in which frontal circulation interacts with copepod behavior to generate a dense patch of copepods. The first two chapters of this thesis address this mechanism in the context of coastal river plumes and salinity fronts. One chapter describes the characteristics and variability of coastal freshwater and salinity fronts using a historical dataset and a realistic numerical model. The seasonal variability of freshwater is tied in part to seasonality in river discharge, while variability on shorter time scales in the frontal position is related to wind stress. Another chapter applies the hypothetical mechanism to idealized river plumes using a suite of numerical models. The structure of the plume and plume-relative circulation change the resulting copepod aggregation from what is expected from the hypothetical mechanism. The second part of the thesis discusses the GOM circulation and how it may eliminate copepod patches. The summertime mean surface circulation and eddy kinetic energy are computed from a Lagrangian drifter dataset and an adaptive technique that allows for higher spatial resolution while also keeping uncertainty low. Eddy diffusivity is also computed over different regions of the GOM in an attempt to quantify the spreading of a patch of copepods, and is found to be lower near the coast where right whales are often found feeding on copepod patches. In the next chapter, a numerical drifter dataset is used to understand how the results of the previous chapter depend upon the quantity of observations. It is found that the uncertainty in estimating eddy diffusivity is tightly coupled to the number of drifters in the calculation. / by Nicholas W. Woods / Ph.D.

Black Buffalo Ictiobus niger are a catostomid species native to the Mississippi River Basin with declining populations. Aquaculture is a common component of recovery plans, however little information is published on catostomid culture methods. This study developed culture techniques for Black Buffalo including tank acclimation, induced spawning, larval rearing, and protein requirements. Fish needed a lengthy acclimation (> 2 months) to reduce signs of stress. After, an induced-spawning protocol was described with gonadotropin-releasing hormone analogue. Swim-up fry did not readily consume zooplankton at first feeding but began selecting for cladocerans one week after stocked in a rearing pond. The juvenile growth study found diets containing 41% crude protein are optimal for growth. Finally, trematodes harm catfish production, and Black Buffalo are a potential control option for catfish producers. However, Black Buffalo did not consume snails, the trematode’s intermediate host, suggesting they would not be an effective trematode control.

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