Abstract:Citation: Santora, J. A., and W. J. Sydeman. 2015. Persistence of hotspots and variability of seabird species richness and abundance in the southern California Current. Ecosphere 6(11):214. http://dx.doi.org/10.1890/ES14-00434.1Abstract. Aggregations of seabirds at sea may provide information on centers of enhanced trophic interactions and concentrating mechanisms, however, to date most studies lack quantification of persistence, a key hotspot characteristic. Persistence statistics may reduce uncertainty about… Show more
“…In order to fully explore the hotspot spectrum and prioritize candidate areas for protection more robustly, a conceptual shift is warranted whereby hotspots are no longer defined in purely geographical terms, but are rather mapped in the four dimensions of latitude, longitude, time and depth, with explicit evaluations of their levels of intra/inter‐annual variability (Santora & Veit, ). Despite being essential to long‐term resource management, such evaluations of hotspot persistence are seldom attempted in practice (Santora & Sydeman, ). A natural way of quantifying the consistency of hotspots through time is to determine the frequency with which a given site exceeds a chosen hotness level.…”
Aim
Protected areas have become pivotal to the modern conservation planning toolbox, but a limited understanding of marine macroecology is hampering their efficient design and implementation in pelagic environments. We explored the respective contributions of environmental factors and human impacts in capturing the distribution of an assemblage of commercially valuable, large‐bodied, open‐water predators (tunas, marlins and mackerels).
Location
Western Australia.
Time period
1997–2006.
Major taxa studied
Pelagic fishes.
Methods
We compiled 10 years of commercial fishing records from the Sea Around Us Project and derived relative abundance indices from standardized catch rates while accounting for confounding effects of effort, year and gear type. We used these indices to map pelagic hotspots over a 0.5°‐resolution grid and built random forests to estimate the importance of 33 geophysical, oceanographic and anthropogenic predictors in explaining their locations. We additionally examined the spatial congruence between these hotspots and an extensive network of marine reserves and determined whether patterns of co‐occurrence deviated from random expectations using null model simulations.
Results
First, we identified several pelagic hotspots off the coast of Western Australia. Second, geomorphometrics explained up to 50% of the variance in relative abundance of pelagic fishes, and submarine canyon presence ranked as the most influential variable in the North bioregion. Seafloor complexity, geodiversity, salinity, temperature variability, primary production, ocean energy, current regimes and human impacts were also identified as important predictors. Third, spatial overlap between hotspots and marine reserves was limited, with most high‐abundance areas primarily found in zones where anthropogenic activities are subject to few regulations.
Main conclusions
This study reveals geomorphometrics as valuable indicators of the distribution of mobile fish species and highlights the relevance of harnessing static topography as a key element in any blueprint for ocean zoning and spatial management.
“…In order to fully explore the hotspot spectrum and prioritize candidate areas for protection more robustly, a conceptual shift is warranted whereby hotspots are no longer defined in purely geographical terms, but are rather mapped in the four dimensions of latitude, longitude, time and depth, with explicit evaluations of their levels of intra/inter‐annual variability (Santora & Veit, ). Despite being essential to long‐term resource management, such evaluations of hotspot persistence are seldom attempted in practice (Santora & Sydeman, ). A natural way of quantifying the consistency of hotspots through time is to determine the frequency with which a given site exceeds a chosen hotness level.…”
Aim
Protected areas have become pivotal to the modern conservation planning toolbox, but a limited understanding of marine macroecology is hampering their efficient design and implementation in pelagic environments. We explored the respective contributions of environmental factors and human impacts in capturing the distribution of an assemblage of commercially valuable, large‐bodied, open‐water predators (tunas, marlins and mackerels).
Location
Western Australia.
Time period
1997–2006.
Major taxa studied
Pelagic fishes.
Methods
We compiled 10 years of commercial fishing records from the Sea Around Us Project and derived relative abundance indices from standardized catch rates while accounting for confounding effects of effort, year and gear type. We used these indices to map pelagic hotspots over a 0.5°‐resolution grid and built random forests to estimate the importance of 33 geophysical, oceanographic and anthropogenic predictors in explaining their locations. We additionally examined the spatial congruence between these hotspots and an extensive network of marine reserves and determined whether patterns of co‐occurrence deviated from random expectations using null model simulations.
Results
First, we identified several pelagic hotspots off the coast of Western Australia. Second, geomorphometrics explained up to 50% of the variance in relative abundance of pelagic fishes, and submarine canyon presence ranked as the most influential variable in the North bioregion. Seafloor complexity, geodiversity, salinity, temperature variability, primary production, ocean energy, current regimes and human impacts were also identified as important predictors. Third, spatial overlap between hotspots and marine reserves was limited, with most high‐abundance areas primarily found in zones where anthropogenic activities are subject to few regulations.
Main conclusions
This study reveals geomorphometrics as valuable indicators of the distribution of mobile fish species and highlights the relevance of harnessing static topography as a key element in any blueprint for ocean zoning and spatial management.
“…Contour lines are the 200‐, 1000‐, and 2000‐m isobaths. Figure derived from Santora and Sydeman (). (Color figure can be viewed at wileyonlinelibrary.com. )…”
Section: Methodsmentioning
confidence: 99%
“…Data were gridded (55 cells; each cell ~4500 km 2 ) to integrate continuous sampling of seabirds with station samples; the gridding procedure was predetermined by the extent of continuous shipboard survey effort (Santora and Sydeman ). If more than one station was sampled per cell, then the mean of all stations sampled was calculated; generally two stations occurred in coastal grid cells due to the sampling design (McClatchie ).…”
Section: Methodsmentioning
confidence: 99%
“…To date, most studies of pelagic hotspots lack estimation of persistence , a key statistic based on the frequency of positive standardized anomalies that provides information on the likelihood of hotspot recurrence (Suryan et al. , Santora and Sydeman , Welch et al. ).…”
Human impacts (e.g., fishing, pollution, and shipping) on pelagic ecosystems are increasing, causing concerns about stresses on marine food webs. Maintaining predator-prey relationships through protection of pelagic hotspots is crucial for conservation and management of living marine resources. Biotic components of pelagic, plankton-based, ecosystems exhibit high variability in abundance in time and space (i.e., extreme patchiness), requiring investigation of persistence of abundance across trophic levels to resolve trophic hotspots. Using a 26-yr record of indicators for primary production, secondary (zooplankton and larval fish), and tertiary (seabirds) consumers, we show distributions of trophic hotspots in the southern California Current Ecosystem result from interactions between a strong upwelling center and a productive retention zone with enhanced nutrients, which concentrate prey and predators across multiple trophic levels. Trophic hotspots also overlap with human impacts, including fisheries extraction of coastal pelagic and groundfish species, as well as intense commercial shipping traffic. Spatial overlap of trophic hotspots with fisheries and shipping increases vulnerability of the ecosystem to localized depletion of forage fish, ship strikes on marine mammals, and pollution. This study represents a critical step toward resolving pelagic areas of high conservation interest for planktonic ecosystems and may serve as a model for other ocean regions where ecosystem-based management and marine spatial planning of pelagic ecosystems is warranted.
“…If the immediate concern is the conservation of populations, then the description of species associations, their frequency and persistence is of immediate value, and such data are not difficult to acquire from dedicated ship-board observations (Camphuysen and Webb, 1999;Veit, 1999;Thiebot and Weimerskirch, 2013;Santora and Sydeman, 2015). We need additional data on interactions among seabirds and other marine predators.…”
There is increasing recognition of the importance of "positive interactions" among species in structuring communities. For seabirds, an important kind of positive interaction is the use of birds of the same species, birds of other species, and other marine predators such as cetaceans, seals and fishes as cues to the presence of prey. The process by which a single bird uses, say, a feeding flock of birds as a cue to the presence of prey is called "local enhancement" or "facilitation." There are subtly different uses of each of these terms, but the issue we address here is the ubiquity of positive interactions between seabirds and other marine predators when foraging at sea, and whether as a result of their associations the feeding success, and therefore presumably the fitness, of individual seabirds is increased. If this contention is true, then it implies that conservation of any one species of seabird must take into consideration the status and possible conservation of those species that the focal species uses as a cue while foraging. For example, conservation of great shearwaters (Ardenna gravis), which often feed over tuna (e.g., Thunnus) schools, should take in to consideration conservation of tuna. Ecosystem management depends on understanding the importance of such processes; the loss of biodiversity, and the consequent threat to foraging success, may be a substantial threat to the stability of marine ecosystems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
