Mesoscale structure and oceanographic determinants of krill hotspots in the California Current: Implications for trophic transfer and conservation

Santora, Jarrod A.; Sydeman, William J.; Schroeder, Isaac D.; Wells, Brian K.; Field, John C.

doi:10.1016/j.pocean.2011.04.002

Cited by 100 publications

(168 citation statements)

References 72 publications

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“…While progress has been made in projecting large-scale prey resource changes (e.g., Stock et al, 2014;Lefort et al, 2015), marine mammal species such as blue whales (Balaenoptera musculus) show tight coupling to smaller scale oceanographic features (Fiedler et al, 1998;Moore et al, 2002;Croll et al, 2005) associated with high euphausiid (krill) abundance (Santora et al, 2011). Similar relations have been exhibited by bowhead whales (Balaena mysticetus) across the Arctic (Laidre et al, 2007;Citta et al, 2015;George et al, 2015) and North Atlantic right whales (Baumgartner et al, 2003;Baumgartner and Mate, 2005).…”

Section: Marine Mammal Ecology and Climate Changementioning

confidence: 83%

Projecting Marine Mammal Distribution in a Changing Climate

et al. 2017

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Climate-related shifts in marine mammal range and distribution have been observed in some populations; however, the nature and magnitude of future responses are uncertain in novel environments projected under climate change. This poses a challenge for agencies charged with management and conservation of these species. Specialized diets, restricted ranges, or reliance on specific substrates or sites (e.g., for pupping) make many marine mammal populations particularly vulnerable to climate change. High-latitude, predominantly ice-obligate, species have experienced some of the largest changes in habitat and distribution and these are expected to continue. Efforts to predict and project marine mammal distributions to date have emphasized data-driven statistical habitat models. These have proven successful for short time-scale (e.g., seasonal) management activities, but confidence that such relationships will hold for multi-decade projections and novel environments is limited. Recent advances in mechanistic modeling of marine mammals (i.e., models that rely on robust physiological and ecological principles expected to hold under climate change) may address this limitation. The success of such approaches rests on continued advances in marine mammal ecology, behavior, and physiology together with improved regional climate projections. The broad scope of this challenge suggests initial priorities be placed on vulnerable species or populations (those already experiencing declines or projected to undergo ecological shifts resulting from climate Silber et al.Projecting Marine Mammal Distributions changes that are consistent across climate projections) and species or populations for which ample data already exist (with the hope that these may inform climate change sensitivities in less well observed species or populations elsewhere). The sustained monitoring networks, novel observations, and modeling advances required to more confidently project marine mammal distributions in a changing climate will ultimately benefit management decisions across time-scales, further promoting the resilience of marine mammal populations.

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Section: Marine Mammal Ecology and Climate Changementioning

confidence: 83%

Projecting Marine Mammal Distribution in a Changing Climate

et al. 2017

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“…The fishing vessels usually aim to maximize their profit, and even though there are several elements which potentially influence their revenue, the most obvious is predictable high concentrations of krill. High concentrations of krill in association with shelf break areas have been documented in several studies (e.g., Constable and Nicol 2002;Santora et al 2011), and the krill fishing pattern during the last decade shows that a few areas in relation to shelf breaks are subject to a particularly high fishing effort (Nicol et al 2012). Our results show that the depth with highest acoustic densities corresponds with the actual fishing depth, indicating that the ''Saga Sea'' deliberately targets the highest krill concentrations also vertically.…”

Section: Discussionmentioning

confidence: 89%

An Antarctic krill (Euphausia superba) hotspot: population characteristics, abundance and vertical structure explored from a krill fishing vessel

2015

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Antarctic krill (Euphausia superba) aggregate in various ways depending on a range of biological and physical factors. In some areas, typically associated with bathymetric features such as shelf edges and canyons, they may aggregate densely to form hotspots. Despite the importance of such hotspots, their development over time in demographic composition and spatial distribution is not well understood. A fishing vessel during regular operation was used for collection of krill demographic and acoustic data on the shelf northwest of South Orkney Islands. Results show a decrease in the proportion of subadult males, partly reflected in an increase in mature adult males. Concurrently, there was a change in the proportion of males in the sampled population from 0.8 to 0.3, indicating immigration or emigration of krill through the hotspot. A clear trend was observed in the diurnal vertical distribution with deeper and more vertically compact swarms during the day. However, some days displayed very small differences between the day and night distribution and considerable variability in the daytime depth distribution. It was noted that although fishing was carried out during the entire period of the study, there was no obvious trend in the acoustic backscatter, suggesting that the overall krill density was not changing during this period. Using a fishing vessel as a research platform has advantages for understanding the dynamics of the fishery and in quantifying biological and physical processes during actual exploitation of these resources.

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“…The cascading effect from regions of enhanced upwelling to primary productivity and krill abundances is also known to cause substantial patchiness in habitat characteristics between the GOF and Monterey Bay . Spatial variability in simulated growth patterns for juvenile salmon within and across years provides evidence for latitudinal changes in habitat quality that may be associated with a balance between upwelling intensity and offshore/alongshore advection [Santora et al, 2011].…”

Section: Geophysical Research Lettersmentioning

confidence: 99%

Environmental conditions impacting juvenile Chinook salmon growth off central California: An ecosystem model analysis

Fiechter

Huff

Martin

et al. 2015

Geophysical Research Letters

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A fully coupled ecosystem model is used to identify the effects of environmental conditions and upwelling variability on growth of juvenile Chinook salmon in central California coastal waters. The ecosystem model framework consists of an ocean circulation submodel, a biogeochemical submodel, and an individual‐based submodel for salmon. Simulation results indicate that years favorable for juvenile salmon growth off central California are characterized by particularly intense early season upwelling (i.e., March through May), leading to enhanced krill concentrations during summer near the location of ocean entry (i.e., Gulf of the Farallones). Seasonally averaged growth rates in the model are generally consistent with observed values and suggest that juvenile salmon emigrating later in the season (i.e., late May and June) achieve higher weight gains during their first 90 days of ocean residency.

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Mesoscale structure and oceanographic determinants of krill hotspots in the California Current: Implications for trophic transfer and conservation

Cited by 100 publications

References 72 publications

Projecting Marine Mammal Distribution in a Changing Climate

Projecting Marine Mammal Distribution in a Changing Climate

An Antarctic krill (Euphausia superba) hotspot: population characteristics, abundance and vertical structure explored from a krill fishing vessel

Environmental conditions impacting juvenile Chinook salmon growth off central California: An ecosystem model analysis

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