A new growth model for red drum (Sciaenops ocellatus) that accommodates seasonal and ontogenic changes in growth rates

The red drum (Sciaenops ocellatus) is a popular gamefish found throughout the coastal waters of the Gulf of Mexico and along the eastern seaboard as far north as Massachusetts. Juvenile red drum grow extremely rapidly, especially during the warmer months, but adults grow very little. In fact, the change in growth with age is so abrupt that the standard von Bertalanffy curve has proven inadequate— the predicted lengths of younger fish are generally too large and the predicted lengths of older fish too small (see Beckman et al., 1988; Murphy and Taylor, 1990).

Differences in diet of Atlantic bluefin tuna (Thunnus thynnus) at five seasonal feeding grounds on the New England continental shelf

The stomachs of 819 Atlantic bluefin tuna (Thunnus thynnus) sampled from 1988 to 1992 were analyzed to compare dietary differences among five feeding grounds on the New England continental shelf (Jeffreys Ledge, Stellwagen Bank, Cape Cod Bay, Great South Channel, and South of Martha’s Vineyard) where a majority of the U.S. Atlantic commercial catch occurs. Spatial variation in prey was expected to be a primary influence on bluefin tuna distribution during seasonal feeding migrations. Sand lance (Ammodytes spp.), Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus), squid (Cephalopoda), and bluefish (Pomatomus saltatrix) were the top prey in terms of frequency of occurrence and percent prey weight for all areas combined. Prey composition was uncorrelated between study areas, with the exception of a significant association between Stellwagen Bank and Great South Channel, where sand lance and Atlantic herring occurred most frequently. Mean stomach-contents biomass varied significantly for all study areas, except for Great South Channel and Cape Cod Bay. Jeffreys Ledge had the highest mean stomach-contents biomass (2.0 kg) among the four Gulf of Maine areas and Cape Cod Bay had the lowest (0.4 kg). Diet at four of the five areas was dominated by one or two small pelagic prey and several other pelagic prey made minor contributions. In contrast, half of the prey species found in the Cape Cod Bay diet were demersal species, including the frequent occurrence of the sessile fig sponge (Suberites ficus). Prey size selection was consistent over a wide range of bluefin length. Age 2–4 sand lance and Atlantic herring and age 0–1 squid and Atlantic mackerel were common prey for all sizes of bluefin tuna. This is the first study to compare diet composition of western Atlantic bluefin tuna among discrete feeding grounds during their seasonal migration to the New England continental shelf and to evaluate predator-prey size relationships. Previous studies have not found a common occurrence of demersal species or a pre-dominance of Atlantic herring in the diet of bluefin tuna.

Intermingling and seasonal migrations of Greenland halibut (Reinhardtius hippoglossoides) populations determined from tagging studies

A total of 7244 Greenland halibut (Reinhardtius hippoglossoides, Walbaum) were tagged in Greenland waters between 1986 and 1998 to increase information on stock delineations, to clarify migration routes, and to describe the seasonal movements of fjord populations. At present 517 recaptured Greenland halibut have been recorded. For Greenland halibut released in Davis Strait, Baffin Bay, and the fjords of southwestern and eastern Greenland, a substantial portion of recovered fish demonstrated migratory behavior, up to 2500 km, primarily to Denmark Strait between Greenland and Iceland. The recaptured fish provided evidence of intermingling between the population in Denmark Strait and the populations in Davis Strait and the southwest Greenland fjords. These observations support those of other studies that indicate that Greenland halibut inhabiting Davis Strait and the fjords of southwestern and eastern Greenland originate in the spawning grounds west of Iceland. The high mobility of offshore Greenland halibut within Baffin Bay and Davis Strait suggests that Greenland halibut migrate extensively between feeding and spawning areas. Greenland halibut in the fjords of northwestern Greenland appear to be resident in behavior and do not intermingle with offshore or more southerly inshore populations. A seasonal pattern in the recovery of these fish indicates that Greenland halibut aggregate in the inner part of fjords during the second half of the year (when inshore waters are not covered with ice).

Seasonal growth of King George whiting (Sillaginodes punctata) estimated from length-at-age samples of the legal-size harvest

Samples of 11,000 King George whiting (Sillaginodes punctata) from the South Australian commercial and recreational catch, supplemented by research samples, were aged from otoliths. Samples were analyzed from three coastal regions and by sex. Most sampling was undertaken at fish processing plants, from which only fish longer than the legal minimum length were obtained. A left-truncated normal distribution of lengths at monthly age was therefore employed as model likelihood. Mean length-at-monthly-age was described by a generalized von Bertalanffy formula with sinusoidal seasonality. Likelihood standard deviation was modeled to vary allometrically with mean length. A range of related formulas (with 6 to 8 parameters) for seasonal mean length at age were compared. In addition to likelihood ratio tests of relative fit, model selection criteria were a minimum occurrence of high uncertainties (>20% SE), of high correlations (>0.9, >0.95, and >0.99) and of parameter estimates at their biological limits, and we sought a model with a minimum number of parameters. A generalized von Bertalanffy formula with t0 fixed at 0 was chosen. The truncated likelihood alleviated the overestimation bias of mean length at age that would otherwise accrue from catch samples being restricted to legal sizes.

Strong, low frequency (decadal) environmental fluctuations during the 20th century in the North Pacific Ocean, on the Washington coast, and in Puget Sound

At decadal period (10-20 years), dynamic linkage was evident between atmospheric low pressure systems over the North Pacific Ocean and circulation in a Pacific Northwest fjord (Puget Sound). As the Aleutian low pressure center shifts, storms arriving from the North Pacific Ocean deposit varying amounts of precipitation in the mountains draining into the estuarine system; in turn, the fluctuating addition of fresh water changes the density distribution near the fjord basin entrance sill, thereby constraining the fjord's vertical velocity structure. This linkage was examined using time series of 21 environmental parameters from 1899 to 1987. Covariation in the time series was evident because of the strong decadal cycles compared with long-term averages, interannual variability, and seasonal cycles.

Climate variability and Crater Lake water levels

Crater Lake has fluctuated in elevation by 5 meters during the 20th Century. Reasons for these fluctuations were investigated as part of a long-term study of the Crater Lake ecosystem. Lake level changes were found to be closely related to precipitation variations. The lake can be thought of as acting as both a giant precipitation gage and as a large evaporation "pan". Winter snowfall variations are related to variations in the Southern Oscillation Index. Crater Lake offers a unique combination of simple geometry and hydrology, and a long record of supporting data, available nowhere else in the world for a caldera lake.

The Younger Dryas and millenial-scale oceanographic variability in the Sulu Sea, tropical western Pacific

EXTRACT (SEE PDF FOR FULL ABSTRACT): A high resolution, AMS carbon-14-dated sediment record from the Sulu Sea clearly indicates the Younger Dryas climatic event affected the western equatorial Pacific. Presence of the Younger Dryas in the tropical western Pacific indicates this climatic event is not restricted to the North Atlantic nor to high latitudes, but is global in extent.

Radiocarbon record of solar variability and Holocene climatic change in coastal southern California

EXTRACT (SEE PDF FOR FULL ABSTRACT): Pollen analysis and 5 radiocarbon dates for a 687-cm core provide a detailed chronology of environmental change for San Joaquin Marsh at the head of Newport Bay, Orange County, California. Sediment deposition kept pace with sea level rise during the mid-Holocene, but after 4500 years BP, sea water regularly reached the coring site, and salt marsh was the local vegetation. Brief periods of dominance by fresh-water vegetation 3800, 2800, 2300 and after 560 years BP correlate global cooling events and (except the 3800-year BP event) with carbon-14 production anomalies. The coincidence of climate change and carbon-14 anomalies support a causal connection with solar variability, but regardless of the causal mechanism(s) the delta-carbon-14 curves provide a chronology for global, high-frequency climatic change comparable to that of Milankovitch cyclicity for longer time scales.

Regional context of the climate of H.J. Andrews Experimental Forest, Oregon

H.J. Andrews Experimental Forest is a 6400 ha forest of Douglas fir, western hemlock, and Pacific silver fir located in, and typical of, the central portion of the western slope of the Cascade mountain range of Oregon. The forest is one of 19 sites in the Long-Term Ecological Research (LTER) program sponsored by the National Science Foundation. ... Because of the scientific significance of Andrews Forest, it is important to investigate the temporal variability of annual and seasonal temperature and precipitation values at the site and identify past times of anomalous climatic conditions. It is also important to establish quantitatively the relationships between the climate of Andrews Forest and that of its surrounding area and, hence, place the climate of Andrews Forest into its regional context.

The California heat island: seasonal trends in maximum and minimum temperatures

This paper summarizes progress in an ongoing study of California's temperature trends. It supplements studies reported at PACLIM in 1984, 1986, and 1987. ... Objectives of this study are twofold: to examine and map the trends in maximum and minimum temperatures for the warm and cool seasons separately, and to examine regional differences in maximum and minimum temperature trends in California.

Seasonal resolution of laminated sediments in Santa Barbara Basin: its significance in paleoclimatic studies

Sediments in Santa Barbara Basin contain microfossil and sedimentological information that allows reconstruction of major features of the California Current such as water temperature, strength of upwelling, and productivity. ... Until now, investigations of Santa Barbara Basin sediments have utilized analytical techniques that could not resolve seasonal laminae, permitting annual resolution of variations in sediment composition and structure only. ... Based on a successful technique for preparation of epoxy-embedded and highly polished thin-sections that permit economical optical and electron microscope evaluation of laminated sequences, it is our long-term goal to reconstruct, with unprecedented detail, the history of sedimentation processes in the Santa Barbara Basin by developing ultra-high-resolution time series of biotic and detrital proxies.