Likelihood ratio, t-, univariate χ2-, and T2-tests have been proposed to compare von Bertalanffy parameters among stocks. As commonly applied, all of these tests are approximate, with the accuracy of each dependent on the nonlinearity of the von Bertalanffy equation, sample size, and if present, the degree of heterogeneity in the error variances. An empirical comparison of these procedures shows that the likelihood ratio test often differs in outcome from the others. Analysis of the conflicting cases by confidence region comparisons and Monte Carlo simulations almost always resolved the outcome in favor of the likelihood ratio test. The parameter effects component of nonlinearity was found to be the principal factor biasing the t-, univariate χ2-, and T2-tests. Reparameterizations of the von Bertalanffy equation substantially reduced, but did not completely eliminate, conflicting outcomes. It is concluded that the likelihood ratio test is the most accurate of the procedures considered in this study, and whenever possible, it should be the approach of choice.

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Three experiments were carried out in 300 l mesocosms using natural seawater from the Peconic Bays ecosystem, Long Island, New York, to examine the ability of the northern quahog Mercenaria mercenaria to prevent blooms of the brown tide alga Aureococcus anophagefferens. Nutrient enrichment and mixing of the mesocosms was conducted according to previous methods that we have employed to induce brown tides. Treatments with and without clams were examined. Abundances of A. anophagefferens increased dramatically during 8 to 9 d experiments in mesocosms without bivalves (average peak abundances > 600 000 cells ml -1). The brown tide alga constituted > 50% of the total phytoplankton biomass in these mesocosms by the end of the experiment. In contrast, algae in mesocosms with high abundances of clams did not develop brown tides and A. anophagefferens abundances in these mesocosms were 2 orders of magnitude lower. Bivalves not only prevented a buildup of total phytoplankton biomass but also prevented the shift in phytoplankton species composition to dominance by A. anophagefferens observed in treatments without clams. Experiments to test the efficacy of different abundances of clams for preventing blooms of A. anophagefferens demonstrated that population clearance rates by clams of approximately 40% of the mesocosm volume d -1 were sufficient to prevent the buildup of phytoplankton biomass and net population growth of the brown tide alga under the environmental conditions and nutrient enrichment that we employed. This turnover rate by suspension-feeding bivalves is similar to the same magnitude of bivalve filtration pressure estimated for Great South Bay, Long Island more than 2 decades ago, prior to the outbreak of brown tides. We conclude that the feeding activities of northern quahogs in shallow bays can exert considerable control on total phytoplankton biomass in the overlying water column, and specifically on the ability of A. anophagefferens to dominate the phytoplankton assemblage and form brown tides.

ABSTRACT-The goal of this study was to investigate whether shell growth reflects metabolic rate rather than overall or somatic tissue production in the soft shell clam Mya arenarja. This was accomplished by conducting laboratory experiments exposing clams to different levels of food, immersion period and temperature in order to uncouple shell and soft tissue growth, and then determining if shell growth and oxygen consumption remained positively correlated. Soft shell clams were raised in a simulated intertidal system for 2 to 3 w k to acclimate them to experimental conditions. After acclimation. oxygen consumption, a measure of metabolic activity, ingestion rate, a measure of energy intake, shell growth and soft tissue growth were estimated for all individuals. Tissue and shell growth were successfully uncoupled in all experiments In the 2 expenments where significant changes in shell growth, soft tissue growth and oxygen consumption occurred, shell growth was posit~vely correlated to oxygen consumption. Soft tissue growth was either uncorrelated or negatively correlated to oxygen consumption and shell growth. Shell transparency In thin sections increased with metabolic rate, while shell growth line clarity decreased in those treatments most stressful to the clams (i.e. low food level a n d high temperature). Our results are cons~stent with the hypothesis that shell growth is coupled to metabolic activ~ty and IS not a measure of somatic tissue production We suggest that information on physiological rate processes is recorded in the shell of b~valves, and that growth line patterns may be used to reconstruct metabolic rates from field collected individuals

The current paradigm in Alewife Alosa pseudoharengus migrations is shifting from a single reproductive event and rapid movement in and out of freshwater to one that recognizes more nuanced movements and asynchronous batch spawning. In this study, Alewives (n = 72) were acoustically tagged in the Carmans River, Long Island, New York, a small coastal river with restored fish passage. Our objective was to examine fine-scale spatial movements in the tidal and reconnected habitats to identify spawning behavior patterns, including habitat use and spawning periodicity, that can be applied to fishway restoration and species management. Alewives that completed their spawning migration (n = 27) exhibited variability in posttagging trajectories, residency, passage rate, and behavior. The current paradigm consisting of a single upstream migration followed by a downstream migration was only seen in 26% (n = 7) of fish, while 41% (n = 11) deviated from the paradigm and made multiple reversals and numerous movements on and off the spawning grounds. Oscillations spanned from the estuary into the reconnected habitat and resulted in a proportionally large amount of time spent in the estuarine and brackish habitats. Some oscillations also consisted of multiple fishway passage events within a season. Oscillation behavior is likely a naturally occurring spawning strategy that has gone undetected. Consequently, the proportion of individuals of a population that display single versus multiple passage events could result in fishway counts that bias run size estimations and thus population assessments.