Within-Season Homing Movements of Displaced Mature Sunapee Trout (Salvelinus Alpinus) in Floods Pond, Maine

Tagging, displacemenat nd recapture, and ultrasonict racking of displaced mature Sunapee trout (Salvelinusa Ipinus) in Floods Pond, Maine, demonstrated that rapid within-season homing occurs in this relict form of Arctic char. Of the trout displaced about 1.8 km from their spawning ground from 1972 to 1975, 9% to 32% were recaptured one to four times within the same spawning season in trap nets set on the spawning ground. Eight of 14 trout tracked ultrasonically in 1975 homed in 2.5 to 10.0 h. Movements of the homing fish were variable; some trout homed paralleling the shoreline, others homed in open water or used a combination of near-shore and open-water movements. Behavior was similar between the sexes and during day and night, although two fish did begin to move just at sundown. Swimming speeds ranged from 15 to 35 cm s- 1 and averaged about 0 .6 body lengths s -1•. Swimming directions were not influenced by wind and wave direction, nor were swimming speeds within individual tracks influenced by cloud cover, wave height, or water depth. Heavy overcast at night m&y have inhibited movement. Sunapee trout are apparently familiar with the entire lake and travel widely within it. Visual features are postulated as orientational cues, though use of such cues is not clearly demonstrated by our experiments.

Migratory Urge and Gill Na(+),K(+)-ATPase Activity of Hatchery-Reared Atlantic Salmon Smolts from the Dennys and Penobscot River Stocks, Maine

Hatchery-reared Atlantic salmon Salmo salar smolts produced from captive-reared Dennys River and sea-run Penobscot River broodstock are released into their source rivers in Maine. The adult return rate of Dennys smolts is comparatively low, and disparity in smolt quality between stocks resulting from genetic or broodstock rearing effects is plausible. Smolt behavior and physiology were assessed during sequential 14-d trials conducted in seminatural annular tanks with circular flow. "Migratory urge'' (downstream movement) was monitored remotely using passive integrated transponder tags, and gill Na(+),K(+)-ATPase activity was measured at the beginning and end of the trials to provide an index of smolt development. The migratory urge of both stocks was low in early April, increased 20-fold through late May, and declined by the end of June. The frequency and seasonal distribution of downstream movement were independent of stock. In March and April, initial gill Na(+),K(+)-ATPase activities of Penobscot River smolts were lower than those of Dennys River smolts. For these trials, however, Penobscot River smolts increased enzyme activity after exposure to the tank, whereas Dennys River smolts did not, resulting in similar activities between stocks at the end of all trials. There was no clear relationship between migratory urge and gill Na(+),K(+)-ATPase activity. Gill Na(+),K(+)-ATPase activity of both stocks increased in advance of migratory urge and then declined while migratory urge was increasing. Maximum movement was observed from 2 h after sunset through 1 h after sunrise but varied seasonally. Dennys River smolts were slightly more nocturnal than Penobscot River smolts. These data suggest that Dennys and Penobscot River stocks are not markedly different in either physiological or behavioral expression of smolting.

Observations of the Eastern Maine Coastal Current and Its Offshore Extensions in 1994

Cold surface temperatures, reflecting Scotian Shelf origins and local tidal mixing, serve as a tracer of the Eastern Maine Coastal Current and its offshore extensions, which appear episodically as cold plumes erupting from the eastern Maine shelf. A cold water plume emanating from the Eastern Maine Coastal Current in May 1994 was investigated using advanced very high resolution radiometer (AVHRR) imagery, shipboard surveys of physical and biochemical properties, and satellite-tracked drifters. Evidence is presented that suggests that some of the plume waters were entrained within the cyclonic circulation over Jordan Basin, while the major portion participated in an anticyclonic eddy at the distal end of the plume. Calculations of the nitrate transported offshore by the plume show that this feature can episodically export significant quantities of nutrients from the Eastern Maine Coastal Current to offshore regions that are generally nutrient depleted during spring-summer. A series of AVHRR images is used to document the seasonal along-shelf progression of the coastal plume separation point. We speculate on potential causes and consequences of plume separation from the coastal current and suggest that this feature may be an important factor influencing the patterns and overall biological productivity of the eastern Gulf of Maine.

Seasonal Distribution and Movements of Shortnose Sturgeon and Atlantic Sturgeon in the Penobscot River Estuary, Maine

Relatively little is known about the distribution and seasonal movement patterns of shortnose sturgeon Acipenser brevirostrum and Atlantic sturgeon Acipenser oxyrinchus oxyrinchus occupying rivers in the northern part of their range. During 2006 and 2007, 40 shortnose sturgeon (66-113.4 cm fork length [FL]) and 8 Atlantic sturgeon (76.2-166.2 cm FL) were captured in the Penobscot River, Maine, implanted with acoustic transmitters, and monitored using an array of acoustic receivers in the Penobscot River estuary and Penobscot Bay. Shortnose sturgeon were present year round in the estuary and overwintered from fall (mid-October) to spring (mid-April) in the upper estuary. In early spring, all individuals moved downstream to the middle estuary. Over the course of the summer, many individuals moved upstream to approximately 2 km of the downstream-most dam (46 river kilometers [rkm] from the Penobscot River mouth [rkm 0]) by August. Most aggregated into an overwintering site (rkm 36.5) in mid-to late fall. As many as 50% of the tagged shortnose sturgeon moved into and out of the Penobscot River system during 2007, and 83% were subsequently detected by an acoustic array in the Kennebec River, located 150 km from the Penobscot River estuary. Atlantic sturgeon moved into the estuary from the ocean in the summer and concentrated into a 1.5-km reach. All Atlantic sturgeon moved to the ocean by fall, and two of these were detected in the Kennebec River. Although these behaviors are common for Atlantic sturgeon, regular coastal migrations of shortnose sturgeon have not been documented previously in this region. These results have important implications for future dam removals as well as for rangewide and river-specific shortnose sturgeon management.

Dispersal Modeling of Fish Early Life Stages: Sensitivity with Application to Atlantic Cod in the Western Gulf of Maine

As an initial step in establishing mechanistic relationships between environmental variability and recruitment in Atlantic cod Gadhus morhua along the coast of the western Gulf of Maine, we assessed transport success of larvae from major spawning grounds to nursery areas with particle tracking using the unstructured grid model FVCOM (finite volume coastal ocean model). In coastal areas, dispersal of early planktonic life stages of fish and invertebrate species is highly dependent on the regional dynamics and its variability, which has to be captured by our models. With state-of-the-art forcing for the year 1995, we evaluate the sensitivity of particle dispersal to the timing and location of spawning, the spatial and temporal resolution of the model, and the vertical mixing scheme. A 3 d frequency for the release of particles is necessary to capture the effect of the circulation variability into an averaged dispersal pattern of the spawning season. The analysis of sensitivity to model setup showed that a higher resolution mesh, tidal forcing, and current variability do not change the general pattern of connectivity, but do tend to increase within-site retention. Our results indicate strong downstream connectivity among spawning grounds and higher chances for successful transport from spawning areas closer to the coast. The model run for January egg release indicates 1 to 19 % within-spawning ground retention of initial particles, which may be sufficient to sustain local populations. A systematic sensitivity analysis still needs to be conducted to determine the minimum mesh and forcing resolution that adequately resolves the complex dynamics of the western Gulf of Maine. Other sources of variability, i.e. large-scale upstream forcing and the biological environment, also need to be considered in future studies of the interannual variability in transport and survival of the early life stages of cod.

Lability of Proteinaceous Material in Estuarine Seston and Subcellular Fractions of Phytoplankton

The rate of proteolysis of amino acids was used to assess the nutritional lability of various materials making up estuarine seston in 3 Maine, USA, estuaries. Physical separations of subcellular fractions of phytoplankton cells led to higher proteolysis rate constants for the cytoplasmic fraction (>1.2 h(-1)) than for the membrane fraction (0.2 to 1 h(-1)). Whole cells, copepod fecal pellets, bottom sediments, and estuarine seston had overlapping ranges of rate constants of 0.17 to 1.3 h(-1), which were indistinguishable from one another. Protein pools in the seston of these estuaries throughout the seasons were dominated by phytoplankton production and its fresh detrital products. Inverse relationships between proteolysis rate constants for estuarine seston and the ratios of pheopigments to chlorophyll indicates that the average lability of seston decreases with the disappearance of cytoplasmic material in suspension. This kinetic approach to the quality of food resources implies the existence of different pools of digestible protein for estuarine heterotrophs with different gut residence times. Preferential enrichment of membrane components in sestonic detritus may result from the differential lability of proteins in cytoplasm versus membrane components of cells.

Nighttime Catches of Fishes in a Tidal Cove in Montsweag Bay Near Wiscasset Maine

Summer nighttime abundance and localized distribution of fishes in a tidal cove were studied by beach seining for comparison with a previous daytime study. American eels were relatively abundant at night and absent during the day. Alewife, blueback herring, and Atlantic silver-side were more abundant in the cove at night. Although mummichog numbers were greatly reduced at night, they remained an important constituent of the night fauna. Lesser components of the night fauna included Atlantic herring, Atlantic tomcod, smooth flounder, winter flounder, and rainbow smelt.

Phytoplankton and Hydrography of the Kennebec Estuary, Maine, USA

The biomass, abundance and species composition of phytoplankton in the Kennebec estuary, Maine, USA, were investigated in relation to hydrography and Light regime during 7 seasonal survey cruises. The salinity distribution ranged from 32 at the mouth to between 0 and 5 at the head, depending on the magnitude of freshwater discharge at the time of each survey. Maximum Vertical salinity and temperature gradients were observed at the mouth. while local tidal mixing, combined with the freshwater flow, produced a well-mixed water column at the head of the estuary. The middle portion of the estuary was stratified on flooding and ebbing tides, but was vertically well mixed at high and low tides. Phytoplankton biomass was lowest in winter (chlorophyll a approximate to 1 mu g l(-1)) and highest in summer (up to 10 mu g l(-1)) The phytoplankton species assemblages at the seaward and the riverine ends of the estuary were made up of taxa with corresponding salinity preferences. Both cell numbers and biomass (chlorophyll a) exhibited a bimodal distribution along the length of the estuary in the warmer months, with the middle portions of the estuary having depressed phytoplankton standing stocks compared with the seaward and landward ends. This bimodal distribution was related to Light limitation and nutrient regeneration in the middle portion of the estuary and to the production of and advective contributions of phytoplankton from both the freshwater and seaward ends.

Dimethylsulfide (DMS) and Dimethylsulfoniopropionate (DMSP) in Relation to Phytoplankton in the Gulf of Maine

Dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP), in both particulate and dissolved forms, were surveyed during the early spring (March and April) and summer (July) of 1991 in coastal and offshore waters of the Gulf of Maine, USA, along with the hydrography, inorganic nutrients, phytoplankton chlorophyll, and phytoplankton taxonomic composition and abundance. Concentrations as high as 15 nM DMS (in April and July), 208 nM particulate DMSP (in April), and 101 nM dissolved DMSP (in July) were recorded. Total DMSP (dissolved plus particulate) reached 293 nM in a patch of the dinoflagellate Katodinium sp. in April. This is the first report of high DMSP concentrations in temperate waters in early spring associated with any organism other than the prymnesiophyte Phaeocystis pouchetii. There were no correlations between phytoplankton biomass, as measured by chlorophyll a, and DMS, and there were only slight correlations between chlorophyll a and DMSP in either dissolved or particulate form. As previously demonstrated by others, concentrations of intracellular (particulate) DMSP were related more to the presence of specific phytoplankton species rather than to overall phytoplankton biomass. The occurrence of high DMSP and DMS levels in early spring, comparable with or higher than those seen in summer maxima, at a time when bacterial activity is minimal and wind speeds are typically high may result in enhanced air-sea-fluxes of DMS.

Biodiversity and Ecosystem Function in the Gulf of Maine: Pattern and Role of Zooplankton and Pelagic Nekton

This paper forms part of a broader overview of biodiversity of marine life in the Gulf of Maine area (GoMA), facilitated by the GoMA Census of Marine Life program. It synthesizes current data on species diversity of zooplankton and pelagic nekton, including compilation of observed species and descriptions of seasonal, regional and cross-shelf diversity patterns. Zooplankton diversity in the GoMA is characterized by spatial differences in community composition among the neritic environment, the coastal shelf, and deep offshore waters. Copepod diversity increased with depth on the Scotian Shelf. On the coastal shelf of the western Gulf of Maine, the number of higher-level taxonomic groups declined with distance from shore, reflecting more nearshore meroplankton. Copepod diversity increased in late summer, and interdecadal diversity shifts were observed, including a period of higher diversity in the 1990s. Changes in species diversity were greatest on interannual scales, intermediate on seasonal scales, and smallest across regions, in contrast to abundance patterns, suggesting that zooplankton diversity may be a more sensitive indicator of ecosystem response to interannual climate variation than zooplankton abundance. Local factors such as bathymetry, proximity of the coast, and advection probably drive zooplankton and pelagic nekton diversity patterns in the GoMA, while ocean-basin-scale diversity patterns probably contribute to the increase in diversity at the Scotian Shelf break, a zone of mixing between the cold-temperate community of the shelf and the warm-water community offshore. Pressing research needs include establishment of a comprehensive system for observing change in zooplankton and pelagic nekton diversity, enhanced observations of "underknown'' but important functional components of the ecosystem, population and metapopulation studies, and development of analytical modeling tools to enhance understanding of diversity patterns and drivers. Ultimately, sustained observations and modeling analysis of biodiversity must be effectively communicated to managers and incorporated into ecosystem approaches for management of GoMA living marine resources.

Effects of Surface Forcing on Interannual Variability of the Fall Phytoplankton Bloom in the Gulf of Maine Revealed Using a Process-Oriented Model

SeaWiFS (Sea-viewing Wide Field-of-view Sensor) chlorophyll data revealed strong interannual variability in fall phytoplankton dynamics in the Gulf of Maine, with 3 general features in any one year: (1) rapid chlorophyll increases in response to storm events in fall; (2) gradual chlorophyll increases in response to seasonal wind-and cooling-induced mixing that gradually deepens the mixed layer; and (3) the absence of any observable fall bloom. We applied a mixed-layer box model and a 1-dimensional physical-biological numerical model to examine the influence of physical forcing (surface wind, heat flux, and freshening) on the mixed-layer dynamics and its impact on the entrainment of deep-water nutrients and thus on the appearance of fall bloom. The model results suggest that during early fall, the surface mixed-layer depth is controlled by both wind-and cooling-induced mixing. Strong interannual variability in mixed-layer depth has a direct impact on short-and long-term vertical nutrient fluxes and thus the fall bloom. Phytoplankton concentrations over time are sensitive to initial pre-bloom profiles of nutrients. The strength of the initial stratification can affect the modeled phytoplankton concentration, while the timing of intermittent freshening events is related to the significant interannual variability of fall blooms.

Early Life History and a Modeling Framework for Lobster (Homarus Americanus) Populations in the Gulf of Maine

Beginning in the late 1980s, lobster (Homarus americanus) landings for the state of Maine and the Bay of Fundy increased to levels more than three times their previous 20-year means. Reduced predation may have permitted the expansion of lobsters into previously inhospitable territory, but we argue that in this region the spatial patterns of recruitment and the abundance of lobsters are substantially driven by events governing the earliest life history stages, including the abundance and distribution of planktonic stages and their initial settlement as Young-of-Year (YOY) lobsters. Settlement densities appear to be strongly driven by abundance of the pelagic postlarvae. Postlarvae and YOY show large-scale spatial patterns commensurate with coastal circulation, but also multi-year trends in abundance and abrupt shifts in abundance and spatial patterns that signal strong environmental forcing. The extent of the coastal shelf that defines the initial settlement grounds for lobsters is important to future population modeling. We address one part of this definition by examining patterns of settlement with depth, and discuss a modeling framework for the full life history of lobsters in the Gulf of Maine.

Summer Abundance of Fishes in a Maine Tidal Cove with Special Reference to Temperature

The daytime abundance and localized distribution of fishes in relation to temperature were studied in a small tidal cove by beach seining on seven dates in the Back River estuary, Maine, during the summers of 1971 and 1972. Temperatures on the seven dates ranged from 15.1–26.2 C, and salinities ranged from 17.3–24.7‰. Eighteen species of fishes were captured, with mummichogs, smooth flounders, Atlantic silversides and Atlantic herring together comprising over 98% of the catch. Mummichogs and Atlantic silversides were captured primarily near the inner end of the cove, while other abundant species were caught mainly at the outer end of the cove. Several species seem well adapted to naturally warm cove temperatures. Others seem now virtually excluded because of warm temperatures. Winter flounder, Atlantic herring, and Atlantic tomcod might be excluded from the cove during daytime in summer if artificial warming of the cove were permitted.

Distribution of Pelagic Fishes in Sheepscot River-Back River Estuary, Wiscasset, Maine

Fifteen species of pelagic fishes were collected in 156 gill net sets at eight locations in the Sheepscot River-Back River estuary, Wiscasset, Maine, June 1970 through December 1971. Highest catches occurred June through August. Only the rainbow smelt is a year-round resident. Differences in abundance in space and time are apparently related to temperature. During the summer, alewives, blueback herring, and Atlantic menhaden were most abundant in the relatively warm Back River estuary, while Atlantic herring, Atlantic mackerel, and spiny dogfish were most abundant in the more oceanic Sheepscot River estuary. Prolonged near-freezing temperatures apparently limit the time pelagic fishes spend in the estuary and limit the number of species which can inhabit it. It is hypothesized that the distribution of pelagic species which exhibited preferences for colder water, such as Atlantic herring, would be most affected by artificial warming of the surface waters of the Back River estuary, if a new atomic powered generating plant were allowed to discharge heated effluent directly into it.

Impacts of Technology Adoption: Comparing Returns to the Farming Sector in Maine under Alternative Technology Regimes

This thesis tests if certain technology choices are associated with a reduction in the proportion of farming activities in the agro-food system in Maine. Goodman, Sorj, and Wilkinson define appropriationism as the replacement of farming sector activities by industrial inputs. Based on the concept of appropriationism, industrial fanning systems using large amounts of synthetic inputs contribute less to fanning than more agrarian systems, like organic fanning. Thus, returns to the farming sector should be greater for organic compared with conventional potato fanning in Maine since organic farming uses fewer industrial inputs. Goodman et. al. define substitutionism as the displacement of farming sector commodities and activities by industrial processes in the marketing sector. Based on the concept of substitutionism, returns to the farming sector should be greater for Lay's Classic®™ potato chips made from natural potatoes compared with Baked Lay's®™ potato crisps manufactured from processed dehydrated potatoes. Returns to the farming sector are defined as returns to the farmer or farm family from farming activities, returns to farm labor, and returns to farmers and farm labor producing inputs used on the farm. Results show absolute returns to the farming sector are less for organic compared to conventional tablestock potato farms in Maine. However as a proportion of farm revenues, large organic farms that market at least 25% of their produce to retail stores or directly to consumers do as well as conventional farms. When comparing returns as a proportion of consumer expenditures, these organic farms do better than conventional farms. Returns to the farming sector are less for organic because of yield penalties, cost of marketing services, and diseconomies of size for organic tablestock potato farms. Expanding acreage and reintegrating livestock with cropping systems may increase returns to the fanning sector. Organic farming demonstrates difficulties in providing marketing services at the farm level. Providing marketing services limits the ability to expand production to capture economies of size. Maine organic potato farmers emphasize non-monetary values such as supporting sustainable agriculture, self-sufficiency, the intrinsic value of work, and close community and family connections. Returns to the farming sector as a proportion of consumer expenditures are about three times greater for Lay's Classic®™ potato chips than for Baked Lay's®™ potato crisps, since the value that farmers receive for potatoes used to produce dehydrated potato flakes in one pound of crisps is about half of the value that farmers receive for potatoes used to make one pound of chips. However, this assumes farmers assign a cost to producing low-grade potatoes for dehydration proportionate to their value. Premium potatoes are used to produce potato chips. Low-grade potatoes are used to produce the dehydrated potato flakes used to make potato crisps. Returns to the farming sector are slightly greater for potato crisps if no costs are allocated to producing low-grade potatoes for dehydration. A shift in consumer preferences from potato chips to crisps may result in a geographical shift of potato production from Maine to the Pacific Northwest assuming no food-grade dehydration facilities are built in Maine.