George W. Boehlert

Revealing pelagic habitat use: the tagging of Pacific pelagics program

Abstract Tagging of Pacific pelagics (TOPP) is a pilot program of the Census of marine life (CoML) that will lead to understanding of pelagic habitat use by marine vertebrates and large squid in the North Pacific. Taking a multispecies approach, the TOPP project will use a range of electronic tag technologies to put the distribution and behavior of pelagic organisms in the context of the oceanography of the North Pacific. Tag-bearing animals will be used as autonomous ocean profilers to enhance sparse oceanographic observations for vast ocean regions. These autonomous ocean samplers will provide unprecedented coverage of the water column structure of the North Pacific. The temporal and spatial data generated by this project will provide an “organism-eye” view of several interactive oceanic regimes in the North Pacific. Twenty target species, including tunas, sharks, pinnipeds, cetaceans, seabirds, and marine turtles, will be monitored with electronic tags. Animal-collected oceanic data will be assimilated into global ocean databases, complement traditional methodologies and be used to help validate nearshore, regional, and basin scale ocean models. As more environmental information is gathered and delivered from the tagged animals, new insights will be obtained about their individual behaviors, as well as how diverse species have separately evolved to forage, reproduce, and survive in the vast pelagic environment. This multi-disciplinary approach will allow a novel merger of biological and physical data to provide a new understanding of the relationship between the movements and behaviors of marine organisms and oceanographic processes in the eastern North Pacific.

Turbidity enhances feeding abilities of larval Pacific herring, Clupea harengus pallasi

Fishes inhabiting estuaries, rivers, and embayments are subject to turbid conditions. Larvae of many fishes utilize estuaries as nursery areas. For visual plankton feeders such as larval fishes, turbidity may reduce search and reaction distances, resulting in lowered feeding abilities. In this study feeding Pacific herring larvae, Clupea harengus pallasi, were exposed to suspensions of estuarine sediment and Mount Saint Helens volcanic ash at concentrations ranging from 0 mg · l−1 to 8 000 mg · l−1. In all experiments, maximum feeding incidence and intensity occurred at levels of suspension of either 500 mg · l−1 or 1000 mg · l−1 with values significantly greater than controls (0 mg · l−1). Feeding decreased at greater concentrations. The suspensions may enhance feeding by providing visual contrast of prey items on the small perceptive scale used by the larvae. Larval residence in turbid environments such as estuaries may serve to reduce predation from larger, visual planktivores, while searching ability in the small larval perceptive field is not decreased.

POST–the Pacific Ocean salmon tracking project

For most of history, the ocean has remained nearly opaque to study, and it has been difficult to understand where salmon or other marine animals go or how they use the ocean. This greatly limits the ability of oceanographers and fisheries biologists to improve the management of many marine resources. The technical and scientific basis now exists to track the ocean movements of individual marine fish for months or years at a time. In this article, we review how new technologies might be applied to salmon in particular. Our conclusion is that animals as small as juvenile Pacific salmon can be followed for months to years at sea, and thus over great distances. By identifying the migration pathways for individual salmon and specific populations of Pacific salmon, we can establish their ocean foraging grounds. We outline the approaches and initial results from the Census of Marine Life program pacific ocean salmon tracking (POST). The research program involves two distinct aspects: (1) the development of an acoustic array for tracking the movements of Pacific salmon during their shelf-resident phase of the life history and (2) the use of archival (data storage) tags to measure aspects of their local environment and to delineate their open ocean migration pathways off the shelf. We report on some of the preliminary findings from the first year of the field project using acoustic tags.

Carbon assimilation as a function of ingestion rate in larval Pacific herring, Clupea harengus pallasi Valenciennes

During the larval stage, clupeoids and other fishes are characterized by straight, relatively undifferentiated guts. Where it has been studied in detail, the evacuation rate in these larvae appears to be directly related to ingestion rate, which is in turn related to food concentration. Qualitative assessments have suggested that the degree of digestion of food particles is inversely related to the rate of evacuation. In the present study, early larvae of the Pacific herring, Clupea harengus pallasi Valenciennes, were fed for 1 h upon 14C-labelled rotifers, Brachionu splicatilis Muller, and Artemia nauplii at high densities. At the end of 1 h, larvae were transferred to six food densities, ranging from 0 to 10 unlabelled prey · ml−1. After 22 h, larvae were removed from the feeding tanks and sacrificed. The labelled carbon remaining in the larvae as a function of the percent consumed after the 1-h feeding interval was used as an index of carbon assimilation. The percent carbon retained decreased significantly with increasing food concentration. Larval herring thus decrease carbon assimilation from individual food particles at high food densities. The magnitude of increasing ingestion, however, more than compensates for the decreased carbon assimilation, and larvae gain greater total energy under conditions of high food concentration. The results support the suggestion that clupeoid larvae are adapted to utilize high food concentrations associated with plankton patches in the pelagic environment.

Effects of temperature, ration, and fish size on growth of juvenile black rockfish, Sebastes melanops

SynopsisYoung Sebastes melanops live as pelagic larvae and juveniles in offshore waters, recruiting to the nearshore environment at an age of approximately six months. In the summer upwelling season, juveniles may be captured in tidepools and shallow coastal waters, where temperatures may be as low as 8°C, or in shallow estuarine habitats where temperatures reach 18°C. This study was conducted to determine the effects of temperature, ration, and fish size upon growth. Juveniles 35 to 93 mm standard length were acclimated to 7°, 12°, and 18°C and provided four daily rations (nominally 0, 25, 50, and 100% maximum ration); growth and food consumption were monitored over 57 days.Growth in length ranged from −0.023 to 0.314 mm per day, relative growth in weight ranged from −0.689 to 1.495% body weight per day, and gross conversion efficiencies ranged from −13 to 21% among treatments. Under starvation conditions, weight loss increased with increasing temperature. At rations expressed as percent maximum at a given temperature, growth increased with increasing temperature. Maximum relative ration (% body weight per day), however, decreased with decreasing temperature; at equivalent relative rations, growth did not differ significantly among temperatures. Evacuation rates determined at the experimental temperatures suggest that daily ration is limited by digestion rate and that temperature therefore affects energy turnover.Growth was analyzed with multiple regression models with ration, temperature, and initial weight as independent variables. Relative growth increased with increasing initial weight. The model predicts that relative maintenance rations decrease with increasing size. The percentage of full ration represented by maintenance ration is relatively greater for small fish at low temperatures, suggesting a basis for ontogenetic change in thermal optima for growth. The results of this study suggest that thermal environment may have an important effect upon first year growth of juvenile S. melanops.

Recruitment Dynamics of Metamorphosing English sole, Parophorys vetulus, to Yaquina Bay, Oregon

Abstract English sole, Parophrys vetulus , spawn in shelf waters off the west coast of North America and early development occurs in coastal waters. Near metamorphosis, however, larvae recruit to nearshore and estuarine nursery areas, an uncommon life-history feature for a species in this region. Recruitment of larval P. vetulus to Yaquina Bay, Oregon, was sampled with moored nets on a weekly basis. Recruitment began during night flood tides in late February and was characterized by three peaks during the season. Planktonic recruitment continued into June, whereas benthic juveniles began to emigrate from the estuary in late May. The data suggest that two developmental stages of recruits immigrated to Yaquina Bay. The first are newly transforming larvae which enter the bay earliest within each peak of recruitment; peaks of abundance are related to onshore Ekman transport. This transport also brings larvae to shallow areas along the open coast where they settle. These transforming stages are still capable of pelagic swimming activity and continue to recruit to the estuary, typically swimming deeper in the water column than the early stages. Estuarine factors, particularly bottom salinity at the end of ebb tide, are most strongly correlated with recruitment of these stages. It seems that tidal stream transport is the primary mechanism used by English sole to recruit to the estuary, but the mechanism of locating the estuary and timing of entry is relatively complex.

Feeding chronology, daily ration, and the effects of temperature upon gastric evacuation in the pipefish,Syngnathus fuscus

SynopsisFeeding chronology, daily ration, and the effects of temperature upon gastric evacuation were examined in the pipefish,Syngnathus fuscus, from field and laboratory data.S. fuscus displayed a pattern of diurnal feeding, characteristic of syngnathids. Daily ration calculations yielded estimates of 4.0 and 4.4% body weight per day, which are comparable to estimates for other teleosts. Evacuation rate was found to be temperature dependent. with more rapid evacuation with increasing temperature. In addition, evacuation rate was found to be positively correlated with gut content. Slowing of evacuation rate with decreasing gut content may allow for increased assimilation efficiency during periods of low food availability. Daily ration, although controlled by the temperature dependence of evacuation rate, may also be controlled by prey abundance; fish maximize food intake during periods of high prey availability, and maximize upon assimilation during periods of low prey availability.

Environmental and Human Dimensions of Ocean Renewable Energy Development

A number of review articles have synthesized current expert opinion regarding interactions of ocean energy generation technologies with environmental parameters and their potential effects and impacts. Fewer articles have documented such interactions, as operational devices and or demonstration sites at which to make such observations are limited. In this paper, we discuss how the perceived risk or impact of ocean renewable energy development on coastal communities (both the human and marine biological communities) is a function not only of actual physical interactions but also depends on the regulatory environment and how potentially impacted coastal resources are valued by stakeholders. In this paper, we review potential environmental effects of ocean energy, identify applicable federal regulations that address potentially affected ecological components, and highlight observations about stakeholder concerns from experiences in Oregon. Understanding the societal lens through which potential environmental effects are viewed is important for developers to move forward as it will be the regulators and local communities who will determine if projects are permitted.

Abrasive effects of Mount Saint Helens ash upon epidermis of yolk sac larvae of Pacific herring Clupea harengus pallasi

Abstract Larval Pacific herring Clupea harengus pallasi were exposed for 24 h to suspensions of estuarine sediment and volcanic ash from 0 to 8000 mg/litre. The effects of these suspensions on the epidermis of the yolk sac larvae were determined using light and scanning electron microscopy. Examination of the epidermis at specific locations on dorsal and ventral body surfaces showed that the effects were apparent with increasing concentrations of both sediment and ash. The effects of volcanic ash, however, occurred at lower concentrations and were of greater magnitude than those of sediment. Examination of the epidermis of these larvae under the scanning electron microscope revealed puncture-type damage associated with volcanic ash but not estuarine sediment. Thus, in addition to the possible effects of smothering which may occur with fine particulates, the ash particles result in direct mechanical damage to the delicate early larvae. The concentrations where effects were noted were greater than those likely to be observed in the lower Columbia River estuary where the larval herring occur. In upriver locations characterized by higher suspended particulates, delicate larvae of other species may suffer epidermal damage.