Harbour seals responded differently to pulses of out-migrating coho and Chinook smolts

2020 ◽  
Vol 647 ◽  
pp. 211-227
Author(s):  
H Allegue ◽  
AC Thomas ◽  
Y Liu ◽  
AW Trites
Keyword(s):  
Chinook Salmon ◽  
Small Proportion ◽  
Predation Pressure ◽  
Mitigation Strategies ◽  
Fine Scale ◽  
Salish Sea ◽  
Data Loggers ◽  
Harbour Seals ◽  
Tide Height

There is increasing evidence that predation by harbour seals on out-migrating salmon smolts may be responsible for the low return of adult coho and Chinook salmon in the Salish Sea. However, little attention has been given to understanding where and when this predation occurs and the extent to which it might be conducted by few or many seals in the population. We equipped 17 harbour seals with data loggers to track seal movements and used accelerometry to infer prey encounter events (PEEs) following the release of ~384000 coho (May 4, 2015) and ~3 million Chinook (May 14, 2015) smolts into the Big Qualicum River. We found a small proportion (5.7%) of all PEEs occurred in the estuary where salmon smolts entered the ocean—and that only one-quarter of the seals actively fed there. PEE counts increased in the estuary after both species of smolts were released. However, the response of the seals was less synchronous and occurred over a greater range of depths following the release of the smaller-bodied and more abundant Chinook smolts. Harbour seals feeding in the estuary appeared to target coho smolts at the beginning of May but appeared to pursue predators of Chinook smolts in mid-May. PEE counts in the estuary increased as tide height rose and were higher at dusk and night—especially during full moonlight. Such fine-scale behavioural information about harbour seals in relation to pulses of out-migrating smolts can be used to design mitigation strategies to reduce predation pressure by seals on salmon populations.

Fine-scale taxonomic and temporal variability in the energy density of invertebrate prey of juvenile Chinook salmon Oncorhynchus tshawytscha

2020 ◽  
Vol 655 ◽  
pp. 185-198
Author(s):  
J Weil ◽  
WDP Duguid ◽  
F Juanes
Keyword(s):  
Energy Density ◽  
Chinook Salmon ◽  
Temporal Variability ◽  
Energy Content ◽  
Single Point ◽  
Single Species ◽  
Fine Scale ◽  
Temporal Differences ◽  
Juvenile Chinook Salmon ◽  
Juvenile Chinook

Variation in the energy content of prey can drive the diet choice, growth and ultimate survival of consumers. In Pacific salmon species, obtaining sufficient energy for rapid growth during early marine residence is hypothesized to reduce the risk of size-selective mortality. In order to determine the energetic benefit of feeding choices for individuals, accurate estimates of energy density (ED) across prey groups are required. Frequently, a single species is assumed to be representative of a larger taxonomic group or related species. Further, single-point estimates are often assumed to be representative of a group across seasons, despite temporal variability. To test the validity of these practices, we sampled zooplankton prey of juvenile Chinook salmon to investigate fine-scale taxonomic and temporal differences in ED. Using a recently developed model to estimate the ED of organisms using percent ash-free dry weight, we compared energy content of several groups that are typically grouped together in growth studies. Decapod megalopae were more energy rich than zoeae and showed family-level variability in ED. Amphipods showed significant species-level variability in ED. Temporal differences were observed, but patterns were not consistent among groups. Bioenergetic model simulations showed that growth rate of juvenile Chinook salmon was almost identical when prey ED values were calculated on a fine scale or on a taxon-averaged coarse scale. However, single-species representative calculations of prey ED yielded highly variable output in growth depending on the representative species used. These results suggest that the latter approach may yield significantly biased results.

scholarly journals Spatially Clustered Movement Patterns and Segregation of Subadult Chinook Salmon within the Salish Sea

2017 ◽  
Vol 9 (1) ◽  
pp. 1-12 ◽  
Author(s):  
M. C. Arostegui ◽  
J. M. Smith ◽  
A. N. Kagley ◽  
D. Spilsbury-Pucci ◽  
K. L Fresh ◽  
...  
Keyword(s):  
Chinook Salmon ◽  
Movement Patterns ◽  
Salish Sea

Correspondence between scale growth, feeding conditions, and survival of adult Chinook salmon returning to the southern Salish Sea: implications for forecasting

2020 ◽  
pp. 102443
Author(s):  
Andrew M. Claiborne ◽  
Lance Campbell ◽  
Bethany Stevick ◽  
Todd Sandell ◽  
James P. Losee ◽  
...  
Keyword(s):  
Chinook Salmon ◽  
Scale Growth ◽  
Salish Sea

Spatial variability of night temperatures at a fine scale over the Stellenbosch wine district, South Africa

OENO One ◽  
2012 ◽  
Vol 46 (1) ◽  
pp. 1 ◽  
Author(s):  
Valérie Bonnardot ◽  
Victoria Anne Carey ◽  
Malika Madelin ◽  
Sylvie Cautenet ◽  
Zelmari Coetzee ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Minimum Temperature ◽  
Climatic Variability ◽  
Thermal Conditions ◽  
Weather Conditions ◽  
Daily Minimum Temperature ◽  
Daily Maximum ◽  
Climate Modelling ◽  
Fine Scale ◽  
Data Loggers

<p style="text-align: justify;"><strong>Aim</strong>: To improve knowledge of spatial climatic variability in viticultural region at fine scale</p><p style="text-align: justify;"><strong>Methods and results</strong>: Night temperatures recorded at 40 data loggers that were located in the vineyards of the Stellenbosch Wine of Origin District were monitored during different weather conditions during the 2009 grape ripening period (January-March). The daily maximum difference in minimum temperature between the coolest and warmest sites was, on average, 3.2 °C for the three-month period while it reached a difference of 14 °C under radiative conditions (a difference of 1 °C to 2 °C per km and 3 °C per 100 m elevation approximately). Numerical simulations of night temperatures, using a mesoscale atmospheric model, were performed for two weather events over this period. Night temperature fields at 200m resolution were generated, taking large scale weather conditions into account. Data from 16 automatic weather stations were used for validation. Temperature data from the data loggers that were located in the vineyards were used to produce maps of spatial distribution of the daily minimum temperature at a 90m scale by means of multicriteria statistical modelling, which concomitantly took environmental factors into account. Locations with optimum thermal conditions for color and flavor development and maintenance were identified based on average values for the three-month period and for specific weather conditions.</p><p style="text-align: justify;"><strong>Conclusion</strong>: The range of minimum temperatures varied as a function of geographical factors and synoptic weather conditions, which resulted in significant differences in night-time thermal conditions over the wine district, with possible implications for grape metabolism. The great spatial variability within short distances emphasized the difficulty of validating outputs of atmospheric modelling with accuracy. The study showed the importance and relevance of increasing resolution to refine studies on climate spatial variability and to perform climate modelling based on distinguished weather types.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: In the context of climate change, it is crucial to improve knowledge of current climatic conditions at fine scale during periods of grapevine growth and berry ripening in order to have a baseline from which to work when discussing and considering future local adaptations to accommodate to a warmer environnement.</p>

scholarly journals Making progress on bycatch avoidance in the ocean salmon fishery using a transdisciplinary approach

2016 ◽  
Vol 73 (9) ◽  
pp. 2380-2394 ◽  
Author(s):  
Saskia A. Otto ◽  
Sarah Simons ◽  
Joshua S. Stoll ◽  
Peter Lawson
Keyword(s):  
Pacific Northwest ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Fishing Effort ◽  
Fine Scale ◽  
Transdisciplinary Approach ◽  
Stakeholder Collaboration ◽  
Study Region ◽  
Fish Stocks ◽  
Spatio Temporal

Abstract Transdisciplinary research that crosses disciplinary boundaries and includes stakeholder collaboration is increasingly being used to address pressing and complex socio-ecological challenges in the Anthropocene. In fisheries, we see transdisciplinary approaches being employed to address a range of challenges, including bycatch where fine-scale data are collected by fishers to help advance spatial approaches in which fishing effort is shifted away from bycatch hotspots. However, the spatio-temporal overlap of morphologically undistinguishable fish stocks, some of which are depleted, is a major concern for some fisheries, including the Pacific Northwest troll Chinook salmon (Oncorhynchus tshawytscha) fishery. In this study, we develop and evaluate a transdisciplinary approach to avoid bycatch in the commercial Chinook salmon troll fishery off northern and central Oregon. Based on a unique genetic dataset collected by fishers, fine-scale patterns of stock distribution and spatial stock overlap were assessed. Two hotspots of weak Klamath stock in the study region were identified and related to bathymetry. Results were then fed into a simple bioeconomic model to evaluate costs and benefits of reallocating effort under two scenarios of allowable catch of a weak stock (Klamath). The scenarios demonstrate that effort reallocation could lead to a reduction in Klamath catch as well as to increases in net profit, but outcomes depend on the distance from the fleets' home port to the new fishing area. The output of the model at its current stage should be regarded strategically, providing a qualitative understanding of the types of best fleet strategies. Despite some challenges in transdisciplinarity discussed in this study and the present limitations to incorporate fine-scale changes of Chinook salmon stock distributions in management regulations, we contend that this approach to research has the potential to lead to improved management outcomes.

Declining spring usage of core habitat by endangered fish-eating killer whales reflects decreased availability of their primary prey

2018 ◽  
Vol 24 (2) ◽  
pp. 189 ◽  
Author(s):  
Monika W. Shields ◽  
Jimmie Lindell ◽  
Julie Woodruff
Keyword(s):  
British Columbia ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Prey Availability ◽  
The United States ◽  
Killer Whales ◽  
Salish Sea ◽  
Critical Habitat ◽  
Endangered Fish ◽  
The North

The salmon-eating Southern Resident killer whales (Orcinus orca) of the north-eastern Pacific Ocean are listed as endangered both in the United States and Canada. Their critical habitat has been defined as the region of the inland waters of Washington State and British Columbia known as the Salish Sea, where they have traditionally spent much of their time from spring through fall. Using reports from experienced observers to sightings networks, we tracked the daily presence of the Southern Residents in these waters from 1 April to 30 June from 1994 through 2016. We found that the escapement estimates of spring Chinook salmon (Oncorhynchus tshawytscha) on the Fraser River in British Columbia were a significant predictor of the cumulative presence/absence of the whales throughout the spring season. There was also a difference in both whale presence and salmon abundance before and after 2005, suggesting that the crash in Chinook salmon numbers has fallen below threshold where it is worthwhile for the whales to spend as much time in the Salish Sea. The use of the Salish Sea by the Southern Residents has declined in the spring months as they are either foraging for Chinook salmon elsewhere or are shifting to another prey species. In order to continue providing necessary protections to this endangered species, critical habitat designations must be re-evaluated as this population of killer whales shifts its range in response to prey availability.

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