The response of fish larvae to decadal changes in environmental forcing factors off the Oregon coast

We conducted a statistical analysis to characterize the influence of large-scale and local environmental factors on presence-absence, concentration, and assemblage structure of larval fish within the northern California Current (NCC) ecosystem, based on samples collected at two nearshore stations along the Newport Hydrographic line off the central Oregon coast. Data from 1996 to 2005 were compared with historical data from the 1970s and 1980s to evaluate pseudo-decadal, annual, and seasonal variability. Our results indicate that the most abundant taxa from 1996 to 2005 differ from those of earlier decades. Concentrations of the dominant taxa and total larvae were generally greater in the winter ⁄ spring than summer ⁄ fall season. Using generalized additive modeling, variations in presence-absence and concentration of taxa were compared to climate indices such as the Pacific Decadal Oscillation, Northern Oscillation Index, and the multivariate ENSO index and local environmental factors, such as upwelling, Ekman transport, and wind stress curl. Significant relationships were found for various combinations of environmental variables with lag periods ranging from 0 to 7 months. We found that the large-scale climate indices explained more of the variance in larval fish concentration and diversity than did the more local factors. Our results indicate that readily available oceanographic and climate indices can explain variations in the dominant ichthyoplankton taxa in the NCC. However, variation in response among taxa to the environmental metrics suggests additional unknown factors not included in the analysis likely contributed to the observed distribution patterns and larval fish community structure in the NCC

Distribution of early life Pacific halibut and comparison with Greenland halibut in the eastern Bering Sea

Information about spatial distribution patterns during early life stages of fish is key to understanding dispersal trajectories and connectivity from spawning to nursery areas, as well as adult population dynamics. More than 30 years of historical field data were analyzed in order to describe the horizontal and vertical distributions of Pacific halibut early life stages (larvae to juveniles) in the eastern Bering Sea and to compare the distributions between Pacific halibut and Greenland halibut. Our results indicate that spawning for both species likely occurred in Bering and Pribilof canyons, along the slope between the two canyons, and on the eastern side of the Aleutian Islands during winter, but Pacific halibut spawning was protracted until early spring. Larvae of both species rose to shallower depths in the water column as they developed, but Pacific halibut larvae had an abrupt movement toward shallower depths. Geographically, larvae for both species either advected northwestward along the Bering Sea Slope or crossed onto the shelves from the slope regions, but the timing in Pacific halibut larval progression onto the shelf and along the slope was earlier than for Greenland halibut larvae. Pacific halibut juveniles (≤ 90 mm total length (TL)) were mostly found in the inner shelf between Bristol Bay and Nunivak Island, along the Alaskan Peninsula, and in the vicinity of the Pribilof Islands. The range of Greenland halibut juvenile (≤ 90 mm TL) distribution was expanded to south of the Pribilof Islands in the middle shelf and to the inner shelf. Although the two species share some attributes (i.e., spawning location) during early life stages, there were species-specific differences associated with spatial distribution (vertically and horizontally), timing differences in larval progression onto the shelves, pelagic larval duration, and juvenile nursery areas.Keywords: Early life history, Settlement, Distribution, Greenland halibut, Pacific halibut, Eastern Bering Se

Lost in plain sight : the evolution of Oregon's nearshore groundfish trawl fleet

The West Coast groundfish industry collapsed in 2000, but it recovered through the efforts of regulators, scientists and the fleet. Now it is working to rebuild the market and reconnect with a formerly active fishing ground along Oregon’s nearshore. In this report, we define nearshore as the shelf that extends seaward to a depth of 110 fathoms (660 feet). The nearshore is of particular value to flatfish groundfish as a nursery and as settlement habitat. It’s also an important area for the recruitment of many other species of groundfish, which tend to settle within the region, making it a desirable spot for Oregon’s groundfish trawlers (1, 2, 3). Despite this, little research has been conducted on the shallow portions of the shelf (around 30 fathoms – or 180 feet – deep). Many of the details of the ecology, health and processes in these habitats remain poorly understood. The knowledge of people who fish within this region, the challenges they face, and the opportunities they can glean from the reopening of nearshore fishing grounds are also insufficiently explored. With this in mind, our study aimed to gather and synthesize the experiential knowledge of nearshore commercial fishermen into a comprehensive and insightful picture of this place, the fishery and the people who engage with it. Connecting narratives and information on fish stocks, their management and the fleet presents an opportunity to holistically understand the health, value and future of this nearshore fishery. We began by gathering data from commercial trawl logbooks and fish tickets. We also conducted semi-structured interviews with industry participants. Our work provides an opportunity to use this local ecological knowledge (LEK) to enhance scientific ecological knowledge (SEK) and inform regional management, users and citizens about Oregon’s nearshore

Transdisciplinary graduate education in marine resource science and management

In this article we consider the current educational needs for science and policy in marine resource management, and we propose a way to address them. The existing literature on cross-disciplinary education in response to pressing environmental problems is vast, particularly in conservation biology. However, actual changes in doctoral-level marine science programs lag behind this literature considerably. This is in part because of concerns about the time investment in cross-disciplinary education and about the job prospects offered by such programs. There is also a more fundamental divide between educational programs that focus on knowledge generation and those that focus on professional development, which can reinforce the gap in communication between scientists and marine resource managers. Ultimately, transdisciplinary graduate education programs need not only to bridge the divide between disciplines, but also between types of knowledge. Our proposed curriculum aligns well with these needs because it does not sacrifice depth for breadth, and it emphasizes collaboration and communication among diverse groups of students, in addition to development of their individual knowledge and skills.Keywords: experiential learning, transdisciplinary, professional skills, graduate educatio

Climate and demography dictate the strength of predator-prey overlap in a subarctic marine ecosystem

There is growing evidence that climate and anthropogenic influences on marine ecosystems are largely manifested by changes in species spatial dynamics. However, less is known about how shifts in species distributions might alter predatorprey overlap and the dynamics of prey populations. We developed a general approach to quantify species spatial overlap and identify the biotic and abiotic variables that dictate the strength of overlap. We used this method to test the hypothesis that population abundance and temperature have a synergistic effect on the spatial overlap of arrowtooth flounder (predator) and juvenile Alaska walleye pollock (prey, age-1) in the eastern Bering Sea. Our analyses indicate that (1) flounder abundance and temperature are key variables dictating the strength of flounder and pollock overlap, (2) changes in the magnitude of overlap may be largely driven by density-dependent habitat selection of flounder, and (3) species overlap is negatively correlated to juvenile pollock recruitment when flounder biomass is high. Overall, our findings suggest that continued increases in flounder abundance coupled with the predicted long-term warming of ocean temperatures could have important implications for the predator-prey dynamics of arrowtooth flounder and juvenile pollock. The approach used in this study is valuable for identifying potential consequences of climate variability and exploitation on species spatial dynamics and interactions in many marine ecosystems. Copyright: 2013 Hunsicker et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credite

A simulation framework for sub-sampling strategy evaluation in multi-stage sampling designs that accounts for spatially structured traits

Selecting an appropriate and efficient sampling strategy in biological surveys is a major concern in ecological research, particularly when the population abundance and individual traits of the sampled population are highly structured over space. Multi-stage sampling designs typically present sampling sites as primary units. However, to collect trait data, such as age or maturity, only a sub-sample of individuals collected in the sampling site is retained. Therefore, not only the sampling design, but also the sub-sampling strategy can have a major impact on important population estimates, commonly used as reference points for management and conservation. We developed a simulation framework to evaluate sub-sampling strategies from multi-stage biological surveys. Specifically, we compare quantitatively precision and bias of the population estimates obtained using two common but contrasting sub-sampling strategies: the random and the stratified designs. The sub-sampling strategy evaluation was applied to age data collection of a virtual fish population that has the same statistical and biological characteristics of the Eastern Bering Sea population of Pacific cod. The simulation scheme allowed us to incorporate contributions of several sources of error and to analyze the sensitivity of the different strategies in the population estimates. We found that, on average across all scenarios tested, the main differences between sub-sampling designs arise from the inability of the stratified design to reproduce spatial patterns of the individual traits. However, differences between the sub-sampling strategies in other population estimates may be small, particularly when large sub-sample sizes are used. On isolated scenarios (representative of specific environmental or demographic conditions), the random sub-sampling provided better precision in all population estimates analyzed. The sensitivity analysis revealed the important contribution of spatial autocorrelation in the error of population trait estimates, regardless of the sub-sampling design. This framework will be a useful tool for monitoring and assessment of natural populations with spatially structured traits in multi-stage sampling designs