22 research outputs found
Recommended from our members
A guide to Oregon fisheries
A short guide to some of the commonly caught commercial seafood species in Oregon
Recommended from our members
Oregon Commercial Dungeness Crab Fishing : 2017-2018 Directive to Minimize Whale Entanglement Risk
This information sheet educates professional crabbers on best practices to avoid whale entanglement and reduce and recover derelict gear. It also provides information on how and when to report an entanglement
Recommended from our members
Constancy and change in marine predator diets across a shift in oceanographic conditions in the Northern California Current
Variable ocean conditions can greatly impact
prey assemblages and predator foraging in marine ecosystems.
Our goal was to better understand how a change in
ocean conditions influenced dietary niche overlap among
a suite of midtrophic-level predators. We examined the
diets of three fishes and one seabird off central Oregon
during two boreal summer upwelling periods with contrasting
El Niño (2010) and La Niña (2011) conditions.
We found greater niche specialization during El Niño and
increased niche overlap during La Niña in both the nekton
and micronekton diet components, especially in the larger,
more offshore predators. However, only the two smaller,
more nearshore predators exhibited interannual variation in
diet composition. Concurrent trawl surveys confirmed that
changes in components of predator diets reflected changes in the prey community. Using multiple predators across
diverse taxa and life histories provided a comprehensive
understanding of food-web dynamics during changing
ocean conditions
Recommended from our members
Environmental drivers and reproductive consequences of variation in the diet of a marine predator
Ocean conditions can greatly impact lower trophic level prey assemblages in marine ecosystems, with effects of ocean state propagating to higher trophic levels. In many regions throughout their range, common murre (Uria aalge) exhibit narrow dietary breadth in feeding chicks and therefore are vulnerable to recruitment failures of dominant prey species during the breeding season. Contrastingly, common murres nesting in the northern California Current off Oregon, exhibit high species diversity and variability in dominant prey consumed. We studied the diets of common murres over 10 years between 1998 and 2011, a period in which the northern California Current experienced dramatic interannual variability in ocean conditions. Likewise, murre diets off Oregon varied considerably. Interannual variation in murre chick diets was influenced by environmental drivers occurring before and during the breeding season, and at both basin and local scales. While clupeids (likely Pacific herring, Clupea pallasii) were an important diet component throughout the study period, in some years murre diets were dominated by Pacific sand lance (Ammodytes hexapterus) and in other years by osmerids (likely whitebait smelt, Allosmerus elongatus and surf smelt, Hypomesus pretiosus). Years in which the Pacific Decadal Oscillation and local sea surface temperatures were higher during summer also showed elevated levels of clupeids in murre diets, while years with higher North Pacific Gyre Oscillation index values and greater local winter ichthyoplankton biomass had fewer clupeids and more sand lance or smelts. Years with higher values of the Northern Oscillation Index during summer and an earlier spring transition showed higher proportion of smelts in the diets. Nesting phenology and reproductive success were negatively correlated with gradients in sand lance and clupeids, respectively, reflecting demographic consequences of environmental variability mediated through bottom-up food web dynamics.Keywords: Common murre, Ocean condition indices, Yaquina Head, Forage fish, California Current, Prey switchin
Recommended from our members
Fishery-specific solutions to seabird bycatch in the U.S. West Coast sablefish fishery
Bird scaring lines (BSLs) protect longline fishing gear from seabird attacks, save bait, reduce incidental seabird mortality and are the most commonly prescribed seabird bycatch mitigation measure worldwide. We collaborated with fishermen to assess the efficacy of applying BSL regulations from the demersal longline sablefish fishery in Alaska to a similar fishery along the U.S West Coast. In contrast to Alaska, some U.S. West Coast vessels use floats along the line to keep hooks off the seafloor, where scavengers degrade the bait and the target catch. Our results confirmed that BSL regulations from Alaska were sufficient to protect baits from bird attacks on longlines without floats, but not baits on longlines with floats. Longlines with floats sank below the reach of albatrosses (2 m depth) at a distance astern (157.7 m ± 44.8 95% CI) that was 2.3 times farther than longlines without floats (68.8 m ± 37.8 95% CI). The floated longline distance was well beyond the protection afforded by BSLs, which is approximately 40 m of aerial extent. Black-footed albatross attacked floated longlines at rates ten times more (2.7 attacks/1000 hooks, 0.48–4.45 95%CI) than longlines without floats (0.20 attacks/1000 hooks, 0.01–0.36 95% CI). Retrospective analysis of NOAA Fisheries Groundfish Observer Program data suggested that seabird bycatch occurs in a few sablefish longline fishing sectors and a minority of vessels, but is not confined to larger vessels. Analysis also confirmed fishermen testimonials that night setting reduced albatross bycatch by an order of magnitude compared to daytime setting, without reducing target catch. Night setting could be an effective albatross bycatch prevention practice if applied to the U.S. West Coast sablefish longline fishery and provide a practical alternative for vessels that elect to use floated longlines. These results highlight the importance of understanding region-specific longline gear modifications to identify effective bycatch reduction tools and the value of working collaboratively with fishermen to craft solutions
Comparing imaging, acoustics, and radar to monitor Leach’s storm-petrel colonies
Seabirds are integral components of marine ecosystems and, with many populations globally threatened, there is a critical need for effective and scalable seabird monitoring strategies. Many seabird species nest in burrows, which can make traditional monitoring methods costly, infeasible, or damaging to nesting habitats. Traditional burrow occupancy surveys, where possible, can occur infrequently and therefore lead to an incomplete understanding of population trends. For example, in Oregon, during the last three decades there have been large changes in the abundance of Leach’s storm-petrels (Hydrobates leucorhoa), which included drastic declines at some colonies. Unfortunately, traditional monitoring failed to capture the timing and magnitude of change, limiting managers’ ability to determine causes of the decline and curtailing management options. New, easily repeatable methods of quantifying relative abundance are needed. For this study, we tested three methods of remote monitoring: passive acoustic monitoring, time-lapse cameras, and radar. Abundance indices derived from acoustics and imagery: call rates, acoustic energy, and counts were significantly related to traditional estimates of burrow occupancy of Leach’s storm-petrels. Due to sampling limitations, we were unable to compare radar to burrow occupancy. Image counts were significantly correlated with all other indices, including radar, while indices derived from acoustics and radar were not correlated. Acoustic data likely reflect different aspects of the population and hold the potential for the further development of indices to disentangle phenology, attendance of breeding birds, and reproductive success. We found that image counts are comparable with standard methods (e.g., radar) in producing annual abundance indices. We recommend that managers consider a sampling scheme that incorporates both acoustics and imaging, but for sites inaccessible to humans, radar remains the sole option. Implementation of acoustic and camera based monitoring programs will provide much needed information for a vulnerable group of seabirds
Recommended from our members
State of the California Current 2014-15: Impacts of the Warm-Water "Blob"
In 2014, the California Current (~28˚–48˚N) saw average, or below average, coastal upwelling and relatively low productivity in most locations, except from 38˚–43˚N during June and July. Chlorophyll-a levels were low throughout spring and summer at most locations, except in a small region around 39˚N. Catches of juvenile rockfish (an indicator of upwelling-related fish species) remained high throughout the area surveyed (32˚–43˚N). In the fall of 2014, as upwelling ceased, many locations saw an unprecedented increase in sea surface temperatures (anomalies as large as 4˚C), particularly at 45˚N due to the coastal intrusion of an extremely anomalous pool of warm water. This warm surface anomaly had been building offshore in the Gulf of Alaska since the fall of 2013, and has been referred to as the “blob.” Values of the Pacific Decadal Oscillation index (PDO) continued to climb during 2014, indicative of the increase in warm coastal surface waters, whereas the North Pacific Gyre Oscillation index (NPGO) saw a slight rebound to more neutral values (indicative of average productivity levels) during 2014. During spring 2015, the upwelling index was slightly higher than average for locations in the central and northern region, but remained below average at latitudes south of 35˚N. Chlorophyll a levels were slightly higher than average in ~0.5˚ latitude patches north of 35˚N, whereas productivity and phytoplankton biomass were low south of Pt. Conception. Catches of rockfish remained high along most of the coast, however, market squid remained high only within the central coast (36˚–38˚N), and euphausiid abundance decreased everywhere, as compared to the previous year. Sardine and anchovy were nearly absent from the southern portion of the California Current system (CCS), whereas their larvae were found off the coast of Oregon and Washington during winter for the first time in many years. Waters warmed dramatically in the southern California region due to a change in wind patterns similar to that giving rise to the blob in the broader northeast Pacific. For most of the coast, there were intrusions of species never found before or found at much higher abundances than usual, including fish, crustaceans, tunicates and other gelatinous zooplankton, along with other species often indicative of an El Niño. Thus species richness was high in many areas given the close juxtaposition of coastal upwelling-related species with the offshore warm-water intrusive or El Niño-typical taxa. Thus the California Current by 2015 appears to have transitioned to a very different state than previous observations
Recommended from our members
State of the California Current 2013-14: El Niño Looming
In 2013, the California current was dominated by
strong coastal upwelling and high productivity. Indices
of total cumulative upwelling for particular coastal
locations reached some of the highest values on record.
Chlorophyll a levels were high throughout spring and
summer. Catches of upwelling-related fish species were
also high. After a moderate drop in upwelling during fall
2013, the California current system underwent a major
change in phase. Three major basin-scale indicators, the
PDO, the NPGO, and the ENSO-MEI, all changed
phase at some point during the winter of 2013/14. The
PDO changed to positive values, indicative of warmer
waters in the North Pacific; the NPGO to negative values,
indicative of lower productivity along the coast; and
the MEI to positive values, indicative of an oncoming
El Niño. Whereas the majority of the California Current
system appears to have transitioned to an El Niño
state by August 2014, based on decreases in upwelling
and chlorophyll a concentration, and increases in SST,
there still remained pockets of moderate upwelling,
cold water, and high chlorophyll a biomass at various central
coast locations, unlike patterns seen during the
more major El Niños (e.g., the 97–98 event). Catches of
rockfish, market squid, euphausiids, and juvenile sanddab
remained high along the central coast, whereas catches
of sardine and anchovy were low throughout the CCS.
2014 appears to be heading towards a moderate El Niño
state, with some remaining patchy regions of upwelling-driven
productivity along the coast. Superimposed on
this pattern, three major regions have experienced possibly
non-El Niño-related warming since winter: the
Bering Sea, the Gulf of Alaska, and offshore of southern
California. It is unclear how this warming may interact
with the predicted El Niño, but the result will likely be
reduced growth or reproduction for many key fisheries
species
Recommended from our members
State of the California Current 2012–13: No Such Thing as an "Average" Year
This report reviews the state of the California Current System (CCS) between winter 2012 and spring 2013, and includes observations from Washington State to Baja California. During 2012, large-scale climate modes indicated the CCS remained in a cool, productive phase present since 2007. The upwelling season was delayed north of 42ËšN, but regions to the south, especially 33Ëš to 36ËšN, experienced average to above average upwelling that persisted throughout the summer. Contrary to the indication of high production suggested by the climate indices, chlorophyll observed from surveys
and remote sensing was below average along much of
the coast. As well, some members of the forage assemblages
along the coast experienced low abundances in
2012 surveys. Specifically, the concentrations of all lifestages
observed directly or from egg densities of Pacific
sardine, Sardinops sagax, and northern anchovy, Engraulis
mordax, were less than previous years’ survey estimates.
However, 2013 surveys and observations indicate an
increase in abundance of northern anchovy. During winter
2011/2012, the increased presence of northern copepod
species off northern California was consistent with
stronger southward transport. Krill and small-fraction
zooplankton abundances, where examined, were generally
above average. North of 42ËšN, salps returned to
typical abundances in 2012 after greater observed concentrations
in 2010 and 2011. In contrast, salp abundance
off central and southern California increased after a
period of southward transport during winter 2011/2012.
Reproductive success of piscivorous Brandt’s cormorant,
Phalacrocorax penicillatus, was reduced while planktivorous
Cassin’s auklet, Ptychoramphus aleuticus was elevated.
Differences between the productivity of these two seabirds
may be related to the available forage assemblage observed in the surveys. California sea lion pups from
San Miguel Island were undernourished resulting in a
pup mortality event perhaps in response to changes in
forage availability. Limited biological data were available
for spring 2013, but strong winter upwelling coastwide
indicated an early spring transition, with the strong
upwelling persisting into early summer
Recommended from our members
Warrenton Shop at the Dock and Beyond
Map highlighting locations where the public can buy fresh local seafood on the Oregon coast