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

Spatial Scale, Means and Gradients of Hydrographic Variables Define Pelagic Seascapes of Bluefin and Bullet Tuna Spawning Distribution

Seascape ecology is an emerging discipline focused on understanding how features of the marine habitat influence the spatial distribution of marine species. However, there is still a gap in the development of concepts and techniques for its application in the marine pelagic realm, where there are no clear boundaries delimitating habitats. Here we demonstrate that pelagic seascape metrics defined as a combination of hydrographic variables and their spatial gradients calculated at an appropriate spatial scale, improve our ability to model pelagic fish distribution. We apply the analysis to study the spawning locations of two tuna species: Atlantic bluefin and bullet tuna. These two species represent a gradient in life history strategies. Bluefin tuna has a large body size and is a long-distant migrant, while bullet tuna has a small body size and lives year-round in coastal waters within the Mediterranean Sea. The results show that the models performance incorporating the proposed seascape metrics increases significantly when compared with models that do not consider these metrics. This improvement is more important for Atlantic bluefin, whose spawning ecology is dependent on the local oceanographic scenario, than it is for bullet tuna, which is less influenced by the hydrographic conditions. Our study advances our understanding of how species perceive their habitat and confirms that the spatial scale at which the seascape metrics provide information is related to the spawning ecology and life history strategy of each species

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