4 research outputs found
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What Happens if Prey Moves Away? The Story of a Movable Feast
Part of the Hatfield Marine Science Center's Sea Lion exhibit.This public exhibit is about the projected shift in temperature that could be associated with significant movements in the small fishes that make up much of the diet of California sea lions. If they prey moves, perhaps the sea lions will move as well, or perhaps they will change their diets to include other prey
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Circle Hook Performance in the Uruguayan Pelagic Longline Fishery
Circle hooks have been promoted as an alternative to traditional J-hooks in pelagic longline fisheries to minimize bycatch mortality and injury to sea turtles and other marine wildlife. We evaluated the effect of hook type (circle hook vs J-hook) on the catch and length composition of target and non-target species in the Uruguayan pelagic longline fishery, for both American- and Spanish-style longlines. The sample unit used for comparing catches was two consecutive sections of the longline, each with a different hook type. For the American-style longline 39,822 hooks were deployed in 108 paired sections, and for the Spanish-style 45,142 hooks were deployed in 238 paired sections. The catch of albacore tuna, Thunnus alalunga (Bonnaterre, 1788), was higher with circle hooks with both gears. The catch of shortfin mako shark, Isurus oxyrinchus (Rafinesque, 1810), also increased with the use of circle hooks, but only with the American-style longline. A decrease was observed in the catch of pelagic stingray, Pteroplatytrygon violacea (Bonaparte, 1832), with both gears, though it was significant only with the Spanish-style longline. The performance of circle hooks for other target species, such as swordfish, Xiphias gladius (Linnaeus, 1758), and sharks, and for bycatch species including sea turtles and seabirds remains unclear and requires further research
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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
Increasing the uptake of multispecies models in fisheries management
Multispecies models have existed in a fisheries context since at least the 1970s, but despite much exploration, advancement, and consideration of multispecies models, there remain limited examples of their operational use in fishery management. Given that species and fleet interactions are inherently multispecies problems and the push towards ecosystem-based fisheries management, the lack of more regular operational use is both surprising and compelling. We identify impediments hampering the regular operational use of multispecies models and provide recommendations to address those impediments. These recommendations are: (1) engage stakeholders and managers early and often; (2) improve messaging and communication about the various uses of multispecies models; (3) move forward with multispecies management under current authorities while exploring more inclusive governance structures and flexible decision-making frameworks for handling tradeoffs; (4) evaluate when a multispecies modelling approach may be more appropriate; (5) tailor the multispecies model to a clearly defined purpose; (6) develop interdisciplinary solutions to promoting multispecies model applications; (7) make guidelines available for multispecies model review and application; and (8) ensure code and models are well documented and reproducible. These recommendations draw from a global assemblage of subject matter experts who participated in a workshop entitled “Multispecies Modeling Applications in Fisheries Management”.publishedVersio