Research

PNCERS: Natural and Anthropogenic Variability in Northeastern Pacific Coastal Systems—An Integrated Approach to Understand Physical and Human Processes that Affect System Health, Resource Viability, and Management Responses

Principal investigators (PIs): D. Armstrong, R. Hilborn (faculty), D. Huppert (UW Marine Affairs), B. Hickey (UW Oceanography), S. Hanna (Oregon State University), A. Shanks (University of Oregon, Oregon Inst. Marine Biology)

Co-PIs: R. Francis, D. Gunderson, R. Naiman, R. Edwards, J. Orensanz, J. Anderson (faculty), J. Parrish (UW Zoology), T. Leschine (UW Marine Affairs), G. Swartzman (UW Applied Physics Laboratory), R. Johnson (Oregon State University), S. Rumrill, C. Roegner (University of Oregon, Oregon Inst. Marine Biology), and R. Thom (Battelle Marine Sciences Laboratory, Sequim)

Collaborators: NOAA/NMFS-R. McConnaughey (Seattle), T. Wainwright (Newport); EPA-T. DeWitt (Newport); Washington Dep. Ecology-J. Newton (Olympia); and North Carolina State University-D. Eggleston (Raleigh)

Support: Coastal Ocean Program, National Atmospheric and Oceanic Administration; Washington Sea Grant Program under the National Oceanic and Atmospheric Administration, U.S. Dep. Commerce

Demographic concentration of human populations along shorelines of estuaries and open coast has led to exponential proliferation over the last century of cities and communities, centers of commerce, industry and transportation, all arrayed against a growing appreciation of the aesthetic value and ecological vulnerability of these aquatic landscapes. Significant loss of marsh and estuarine tidelands through damming, dredging, diking, landfill, erosion, pollution in a broad context, and encroachment of exotic species have all served as warnings of anthropogenic perturbations in drastically altered systems such as San Francisco Bay and its delta, Chesapeake Bay, and Gulf States wetlands. Societal demands have led to myriad user conflicts regarding resource use and allocation, expectations of constancy and predictability, and dependence on managers to plan, allocate, and perpetuate in a wise fashion that safeguards the intricate blend of ecosystems and human uses and intrusions.

Added to this perspective of multifaceted human activity as cause of change in ecosystems is the growing appreciation of the magnitude of spatial and temporal variation in all natural dimensions of these systems (chemical, physical, biotic) as powerful determinants of change in species populations and ecosystem processes. This mix of planned human activities (harvest, commerce, habitation, tourism, physical alteration for ports, marinas, jetties) and unplanned consequences (pollution, habitat degradation, spread of exotics, species endangerment) has increased need to place managerial decision making related to aquatic systems within a web of inter-linked agency roles and knowledge of ramifications to ecosystems and resources stemming from such decisions. Yet this vision is only tractable to the extent system processes, forcing functions, and scales of variability are known and understood as the backdrop for defining and measuring short- and long-term anthropogenic effects.

Primary goals as we interpret historical background and program description provided by the PNCER Management Team are as follows:

Understand, describe, and model nearshore physical forcing functions with respect to signals of natural variability that occur over scales of days, years and decades, and over kilometers to hundreds of kilometers alongshore.
Portray biotic response to these variables in appropriate units from individual (e.g. reproductive success, growth rates) to populations (e.g. fisheries trends, year class survival) as illustrated by salmon and other pertinent taxa.
Measure and model physical links between nearshore and estuarine systems that highlight types, causes, and magnitude of natural variability.
Understand, describe, and model physical forcing functions within estuaries (e.g. circulation, water structure, watershed and riverine inputs, sedimentation, nutrients).
Catalogue, inventory, and map biotic elements of these systems with respect to habitat, production, seasonal/ontogenetic movements within the physical framework of #4.
Describe, quantify. and map the nature of historical anthropogenic activity in both the biotic and abiotic realms. Provide cause-and-effect links between seemingly disparate human activities as they impinge on natural processes (e.g. logging in watersheds–hydrology–sediment transport–estuarine sedimentary budgets–epibenthic oyster culture) to enhance understanding of possible dendritic spread of perturbations in the natural systems.
Describe and understand human activities and institutions, economics, and resources that may impinge on aquatic systems. Ascertain user perception of relative value and extent of relatedness of various resource bases and human activities.
Blend physical and biological information derived from natural and anthropogenic system perspectives as link of social and economic consequences to actual or predicted ecosystem conditions in order to foretell outcome of management/agency decisions
Provide means to access and use resultant databases, models, and simulations that tie economics and resources to physical and biological systems as tools for managers in a broad context.

Reproductive Dynamics of Female Snow and Tanner Crab Populations in the Eastern Bering Sea

Collaborators: B. Ernst, graduate student, J. Orensanz, faculty

Support: Alaska Dep. Fish & Game

Recent declines in population abundance of both Tanner and snow crabs in the eastern Bering Sea have prompted concerns regarding the health of the stock and the future of the fishery. Mandated by the Magnuson-Stevens fishery Conservation and Management Act, rebuilding plans have been developed for these stocks in an attempt to return abundances to historical levels. Crucial in the success of such management plans is an understanding of the role of reproductive dynamics and stock structure in generating recruitment trends. We propose to use several pieces of information to (1) assess the reproductive dynamics of female snow and Tanner crab stocks from the EBS, (2) determine whether population declines may be due to fishing of the male population to a point at which the female population is below its maximum reproductive capacity, and (3) conduct spatial analyses to examine interactions between stock structure, historical fishing pressure, and summer near-bottom temperature conditions. The work proposed will provide a comprehensive and spatially explicit model of the dynamics of female patterns, recruitment areas, and the configuration of physical gradients used for ontogenic migration that are encountered by a cohort. Our results will provide a framework for understanding such changes, and tailoring management actions to respond to population function.

Ocean—Estuarine Coupling and Material Processing by Oysters

Collaborators: C Roegner; B Hickey, P MacCready (UW Oceanography); J Ruesink (UW Zoology); B Dumbauld (Washington Dep. Fish & Wildlife); J Newton (Washington Dep. Ecology)

Support: Washington Sea Grant Program under the National Oceanic and Atmospheric Administration, U.S. Dep. Commerce

A majority of U.S. West Coast oyster production occurs in Willapa Bay, yet there is evidence of long-term decline since the 1950s in condition indices and reduction in amount of prime historical growing areas. At the same time, proliferating issues under ESA threaten oyster industries via implications of potential perturbation of salmonid habitat caused by aquaculture practices. The proposed work will clarify the broad ecological role of oysters in these systems as links between pelagic and benthic production. Results will help to both predict possible change in oyster condition indices reflective of ocean forcing and gradients in estuarine nutrients and food, and shape culture practices to attenuate severe fluctuations based on a more comprehensive integration of estuarine functions.

Juvenile Dungeness Crab Ecology in Intertidal Shell Mitigation Habitat, Grays Harbor, Washington

Collaborators: E. Visser (graduate student) and D. Eggleston (North Carolina State University)

Support: Washington Sea Grant Program under the National Oceanic and Atmospheric Administration, U.S. Dep. Commerce

The estuarine ecology of Dungeness crab (Cancer magister) was investigated in the context of size- and age-related requirements and shifts in location. Megalopae propagate into estuaries during spring flood tides in tidal intrusion fronts that reach strategic intertidal areas where larvae settle and metamorphose to first juvenile instars. Megalopae most typically occur in surface shell deposits as a result of physical processes that may enhance settlement in response to changes in boundary layer currents and/or active choice between some form of surface topography (e.g., shell, eelgrass) and open mudflats. Initial density is often very high (200–300 m^-2) but quickly declines owing to predation and movements. These surface deposits most typically contain shells of Mya arenaria and cultured Pacific oyster, Crassostrea gigas. After 2–3 months of intertidal residency, 0+ crab (~25–30 mm carapace width) move to the subtidal in late summer.

Evidence of high intertidal production of 0+ juveniles was used as the basis for mitigation of subtidal dredging impacts caused by the US Army Corps of Engineers (USACE) during extensive annual maintenance of the navigation channel. On the basis of our estimates, ~200,000 1+ juveniles would be killed during removal of some 10 million m³ of sediment. The solution was to construct ~16 ha of intertidal oyster shell habitat in 1992 that would enhance settlement and production of sufficient 0+ juveniles (scaled to account for natural mortality) to offset loss of resource caused by the USACE. Subsequent study of crab populations and fate of the habitat has revealed several interesting and unsuspected ecological relationships and consequences:

A large percentage of the shell was rapidly lost as viable crab habitat because it either sank into the mudflat or was sedimented over. Sinkage is linked to high densities of two thallassinid shrimp that dig extensive burrow networks and reduce substrate compaction.

0+ crab within the shell grow rapidly and reach high biomass, seemingly in excess of sessile stocks of prey. Additional food appears to come in the form of mobile fauna, such as gammarid amphipods, and cannibalism of conspecifics.

The faunal composition of shell habitat exhibits changes over time after placement, and in the second year includes the shore crab, Hemigrapsus spp., in high densities. In this situation 0+ Dungeness are at very low densities or non-existent, and we suspect predation by megalopae or competitive displacement directly.

Even if the habitat mitigation works to produce excess 0+ crab, it is not clear that subtidal populations can absorb this "artificial cohort" with respect to available food supplies since the biomass of older subtidal juveniles is very high and perhaps near carrying capacity of the system. These issues are still under study.

Tanner and Snow Crab Research

Reproductive Biology of Snow and Tanner Crab in the Eastern Bering Sea

Collaborators: J. Orensanz, A. Nevissi (faculty) R. Otto, B. Stevens (NMFS, Kodiak), and A. Paul (University of Alaska, Seward)

Support: National Marine Fisheries Service

The Chionoecetes opilio fishery from the eastern Bering Sea is a male-only fishery, and in this respect is similar to other crab fisheries regarding assumptions about reproductive safeguards. Males are polygynic and females can store sperm across years. Given these circumstances, it has been assumed that male escapement is sufficient for survivors to effectively fertilize the reproductive segment of the female population. This paradigm, however, is being increasingly challenged by new findings on complexities in male mating behavior, limits to effective male polygyny, and decline in the viability of stored sperm over time.

We investigated the reproductive contribution of different segments of the female population through the analysis of extensive samples covering much of the region of interest during summer 1992 and 1993. Relative fecundity was scaled to maximum size-specific fecundity, the latter involving the estimation of envelope functions. Fecundity is being analyzed in relation to size, life-history stage (primi- vs. multiparous condition, shell condition indices), geographic location, and distribution of the male population; envelope functions for different categories were compared using randomization techniques. The emergent pattern was compared between years, and a hypothesis has emerged that explains the ontogeny of reproductive activities in the female C. opilio population from the eastern Bering Sea with respect to spatial changes in relationship to condition indices and reproductive output.

Detailed observations were made on the spermathecae and stored sperm of ca. 4,000 females, complemented by the microscopic study of a subsample. The geographic pattern of the inseminates (sperm content of the spermathecae) was analyzed in relationship to location, female condition (primi- vs. multiparous, shell condition indices), and distribution of the male population. Matching between geographic patterns of insemination (old stored and recent sperm), fecundity, and shell condition (apparent shell age) is being explored to test the hypothesis of extensive, life-long ontogenetic migrations across the eastern Bering Sea.

Radiometric Estimation of Shell Age in Tanner Crab

Collaborators: A. Nevissi, J. Orensanz (faculty), and A. Paul (University of Alaska)

Support: National Marine Fisheries Service, through Washington Sea Grant Program under the National Oceanic and Atmospheric Administration, U.S. Dep. Commerce

Estimation of age in crabs, important for the stock assessment of commercially valuable species, is difficult because of the fact that crabs (as well as other crustaceans) shed all their calcified parts at molting. Unlike fish and molluscs, they do not have permanent hard structures on which growth marks are laid down periodically. Radiometric methods have been used to estimate the age of crab shells in at least two published studies, both based on the analysis of a few individuals. Measurements were based on the determination of Th²²⁸/Ra²²⁸ and other isotopic ratios. The basic assumptions for radiometric age determination are that virtually all the calcium and associated nuclides are lost by the animal at the time of molting, the new carapace is calcified rapidly after molting, and there is no chemical addition or removal of radionuclides after calcification.

The purpose of this study was to investigate the possible use of radiometric measurements to assess the meaning (in terms of shell age) of "shell condition indices," which are routinely recorded during annual surveys of crab stocks. Samples of males in each of the five standard shell conditions were collected in two areas of the eastern Bering Sea. Specimens of Tanner crab (Chionoecetes bairdi) of known molting date, kept at the Seward Marine Center, were used for calibration of the technique. Methods were refined for the measurement of Ra²²⁸, Th²²⁸, Ra²²⁶, and Pb²¹⁰. Radiochemical analyses are still in process.

Alternative Methods to Control Burrowing Shrimp Impacting Oyster Culture

Collaborators: K. Feldman (graduate student) and B. Dumbauld (WDFW)

Support: Western Regional Aquaculture Center, U.S. Dep. Agriculture

Survival and growth of the Pacific oyster (Crassostrea gigas) along the Pacific coast of the United States are adversely affected by burrowing ghost shrimp, Neotrypaea californiensis, and mud shrimp, Upogebia pugettensis. In Washington State, the insecticide carbaryl has been applied to oyster beds to control populations of shrimp since 1963. While carbaryl effectively removes shrimp, it has detrimental impacts on non-target species and does not discourage re-invasion by young-of-the-year (YOY) shrimp. We have initiated this study to examine processes that influence shrimp recruitment to intertidal epibenthic shell and mud habitats and to incorporate this information into aquaculture practices to attempt to reduce densities of YOY shrimp on oyster beds.

We found that a thick layer of shell applied to bare mudflat ("shell pavementing") significantly reduced densities of YOY ghost shrimp but not YOY mud shrimp relative to bare mud substrate. In the case of ghost shrimp, the shell only served as an effective barrier if it remained on the surface; in areas where shell sank 5–15 cm into the mud, there was no difference in YOY densities between this "subsurface shell" habitat and bare mud. Recruitment patterns reflected, in part, differential postlarval settlement preferences. Postlarval ghost shrimp preferred to settle in bare mud whereas preliminary results from experiments with mud shrimp suggest that they settle at comparable density in both mud and shell. Juvenile Dungeness crab, which reside in epibenthic shell habitat, preyed on both species of shrimp in laboratory experiments, but there was no evidence that they regulated population densities in shell substrate.

On the basis of our recruitment studies, we designed experiments to test whether shell pavementing might benefit oyster culture by reducing densities of shrimp (particularly ghost shrimp) and improving retention of oyster cultch (shells with small oyster spat). The addition of epibenthic shell to oyster beds reduced densities of YOY ghost shrimp and increased retention of cultch, but only on plots where adult shrimp had first been removed with carbaryl. Shell and oyster cultch sank quickly into the sediment on plots where adult shrimp were still present, and did not reduce recruitment of YOY ghost shrimp compared with control plots. Epibenthic shell did not reduce densities of YOY mud shrimp but did increase retention of oyster cultch compared with control plots. Our studies suggest that incorporating shell pavementing into oyster culture practices might be beneficial on some oyster beds, particularly where ghost shrimp are present. Although carbaryl would still need to be sprayed initially to remove existing shrimp, the long-term frequency of pesticide application might be reduced if epibenthic shell habitat persisted.

Population Size and Life History Parameters of the Everglades Crayfish

Collaborators: N. Hendrix (graduate student), C. Grue (faculty), and B. Loftus (National Biological Service, Florida)

Support: National Biological Service through the SoF Washington Cooperative Fish and Wildlife Research Unit

Freshwater macroinvertebrates are important and abundant animals in the Everglades/Big Cypress system and, as such, are critical in the transfer of energy through the system. The ecology and life histories of the invertebrates are intimately tied to the hydrology of the marsh, which is determined mainly by rainfall, but increasingly by water management practices. The Everglades crayfish (Procambarus alleni Faxon) is found in a variety of Everglades fresh and brackish water habitats in which it is consumed by a host of predators. While several species of wading birds consume P. alleni almost exclusively, little is known about the biology and ecology of the species. Thus, under the umbrella of an ecosystem level model entitled ATLSS (Across Trophic Level System Simulation), density estimates and life history parameters of P. alleni were collected in three areas of the Everglades/Big Cypress system throughout 1996.

In addition to discovering P. alleni , we found an additional species, Procambarus fallax, which was collected in longer hydroperiod habitats (inundated for greater than 9 mo yr^-1). Distribution of P. alleni appears to coincide with shorter hydroperiod locations (inundated 3–5 mo yr^-1) with some overlap between the two species in areas that are intermediate to these hydroperiods. While combined density estimates have been collected for both species during sampling events in February and July (due to the oversight that we were collecting two species), the November sampling event was conducted with regard to species composition. In the final year of sampling, we intend to further characterize the habitat requirements of each species as well as investigate potential differences in sensitivity to hydrology, which could be influenced through water management practices.

Recruitment Limitation in Red King Crab: The Importance of Early Life Stages

Collaborators: T. Loher (graduate student) and R. Francis (faculty)

Support: Saltonstall–Kennedy Grant, National Marine Fisheries Service

The collapse of the Alaskan red king crab (Paralithodes camtschaticus) fisheries of the eastern Bering Sea and Northern Gulf of Alaska, once viewed as the result of overfishing and stock mismanagement, was most likely the result of larger-scale processes we do not yet understand. It is clear that substantial recruitment variability has been operating on this stock and that a better understanding of the processes that regulate crab stocks is needed. In order to understand recruitment dynamics of red king crab, we need to identify the life-history phase that limits recruitment to fishable stocks. Evidence suggests that survivorship through early benthic stages is critical in determining subsequent stocks, and that the availability and quality of juvenile nursery habitat may be the "bottleneck" through which many benthic crustacean populations must pass.

Our present research focuses on clarifying the role of benthic nursery habitat and its carrying capacity in determining overall recruitment to the fishery. Field studies were conducted during summer 1997 in Auke Bay, Southeast Alaska, to determine the physical nature of preferred settlement habitat in relationship to larval supply. Suction-dredge sampling was employed in late spring to survey for the presence of early benthic phase ("EBP"; age 0–2 years) crab in various habitat types. Throughout the summer, settlement studies were conducted to determine whether EBP crab abundance patterns are the result of larval supply, active choice of habitat by settling or post-settlement crab, or the elimination of crab from suboptimal habitat by post-settlement processes. Study sites were established and monitored in shallow water (approximately 8 m), via SCUBA, in habitats characterized by three discretely different substrate types (flat muddy bottom, sandy bottom mixed with broken shell–hash, and complex rocky bottom) while larval supply was monitored throughout the study area. Preliminary data analysis suggests that spatial abundance patterns of EBP crab differ greatly from larval abundance patterns, suggesting that processes at or shortly after settlement are critical in determining early recruitment levels. Homogenous or soft-bottom habitat are generally devoid of new settlers and EBP crab, even where larval densities above the substrate are high. Conversely, lower levels of larval supply overlying rocky habitat result in significant recruitment of age 0 crab and retention of red king crab populations at least through age 2.

The ramifications of such processes may be great. Much of the Bering Sea and Bristol Bay is characterized by homogenous mud and sand bottom, while areas of shell hash, cobble, and three-dimensional biogenic structure are highly limited. As such, much of the annual larval supply generated by breeding populations of red king crab may be delivered to habitat that is inadequate for the survival of early benthic individuals. These larvae, while considered by various fishery models as eventual members of the fishable stock, may be completely lost to predation or starvation near settlement. Clearly, in a case such as this, it is critical not only to know the potential larval supply from a given breeding stock and the expected planktonic survival rates, but also what proportion of those larvae are delivered to suitable habitat and what proportion may be expected to perish shortly after settlement. Future work in this project will focus on establishing the quality and spatial distribution of potential Bering Sea red king crab nursery habitat, and on determining the relationship between distribution of breeding stocks and delivery of larvae to suitable nursery sites.

Potential Impacts of An Exotic Crab on Selected West Coast Commercial Invertebrates

Collaborators: G. Jensen (graduate student), E. Grosholz (University of California Davis), G. Ruiz (Smithsonian Environmental Research Lab, Maryland), and G. Jamieson (Pacific Biological Station, Nanaimo, British Columbia)

Support: Washington Sea Grant Program under the National Oceanic and Atmospheric Administration, U.S. Dep. Commerce

The presence of the European green crab, Carcinus maenas, on the west coast of the United States portends significant ecological impact in estuarine and marine systems. In addition to broad-scale community interactions, Carcinus will likely prey on juvenile and subadult stages of certain commercial invertebrates. We propose to study Carcinus' response to two categories of invertebrate prey, mobile Dungeness crab (Cancer magister) and sessile bivalves, in order to gauge the potential ability of this exotic crab to significantly perturb populations and cause resultant economic loss to fisheries and aquaculture industries. In cooperation with scientists in California who are studying the general ecology and predatory role of Carcinus, we will conduct experiments in the lab and field with a focus on important substrates such as bivalve shell and gravel used as refuge habitat to mitigate various environmental impacts or to improve commercial production. We will study (1) predation by Carcinus on 0+ C. magister in shell, including whether C. magister emigrate (escape) from shell habitat occupied by the predator; (2) predation by larger 1+ C. magister on Carcinus to indicate whether an indigenous predator at high biomass might limit population distribution; (3) colonization of shell plots in situ and resulting seasonal and tidal dominance where populations of at least three crab (Carcinus, C. magister, and the shore crab Hemigrapsus oregonensis) co-occur; (4) size-specific rates of predation and upper size limits of two bivalve prey, Manila clams and Pacific oysters, as a function of crab size and habitat cover; (5) prey preference in limited experiments using a mix of clams, oysters, and barnacles; and (6) stomach contents of Carcinus captured in situ with focus on bivalves and crab.