Periodic variability in cetacean strandings: links to large-scale climate events

Evans, Karen; Thresher, Ronald E.; Warneke, Robert M; Bradshaw, Corey J. A.; Pook, Michael J.; Thiele, Deborah; Hindell, Mark A.

doi:10.1098/rsbl.2005.0313

Cited by 117 publications

(108 citation statements)

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“…Military sonar use, for example, has been implicated in some cetacean strandings [10]; marine pollution, geomagnetic interference and geomorphological features have also been considered as putative mechanisms [11,12]. More convincingly, changes in prey resources demonstrably drive stranding occurrences, and regions with mass stranding 'hotspots' are linked with cyclical large-scale oceanographic and climatic variables [13,14].…”

Section: Introductionmentioning

confidence: 99%

The high fidelity of the cetacean stranding record: insights into measuring diversity by integrating taphonomy and macroecology

Pyenson

2011

Proc. R. Soc. B.

101

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Stranded cetaceans have long intrigued naturalists because their causation has escaped singular explanations. Regardless of cause, strandings also represent a sample of the living community, although their fidelity has rarely been quantified. Using commensurate stranding and sighting records compiled from archived datasets representing nearly every major ocean basin, I demonstrated that the cetacean stranding record faithfully reflects patterns of richness and relative abundance in living communities, especially for coastlines greater than 2000 km and latitudinal gradients greater than 48. Live-dead fidelity metrics from seven different countries indicated that strandings were almost always richer than live surveys; richness also increased with coastline length. Most death assemblages recorded the same ranked relative abundance as living communities, although this correlation decreased in strength and significance at coastline lengths greater than 15 000 km, highlighting the importance of sampling diversity at regional scales. Rarefaction analyses indicated that sampling greater than 10 years generally enhanced the completeness of death assemblages, although protracted temporal sampling did not substitute for sampling over longer coastlines or broader latitudes. Overall, this global live -dead comparison demonstrated that strandings almost always provided better diversity information about extant cetacean communities than live surveys; such archives are therefore relevant for macroecological and palaeobiological studies of cetacean community change through time.

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Section: Introductionmentioning

confidence: 99%

The high fidelity of the cetacean stranding record: insights into measuring diversity by integrating taphonomy and macroecology

Pyenson

2011

Proc. R. Soc. B.

101

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“…Mass strandings, which are almost entirely restricted to toothed cetaceans, have been explained by a similar list of causes, but the striking peculiarity of entire stranded pods, which can consist of hundreds of individuals, has produced no shortage of hypotheses. Explanations for mass strandings include geomagnetic interference with navigation (Kirschvink 1990;Walker et al 1992); complexities of nearshore geomorphology (Brabyn and Frew 1994); military sonar use (Cox et al 2006;Parsons et al 2008); and large-scale patterns in earth and ocean climate (Evans et al 2005;Bradshaw et al 2006). This list of possible mechanisms is not mutually exclusive, and the putative causes for strandings vary in explanatory power depending on the number of individuals stranded, the region in which the events occur, as well as any obvious anthropogenic causes (e.g., ship strikes [Douglas et al 2008]).…”

Section: Introductionmentioning

confidence: 99%

Carcasses on the coastline: measuring the ecological fidelity of the cetacean stranding record in the eastern North Pacific Ocean

Pyenson¹

2010

Paleobiology

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Abstract.-To understand how well fossil assemblages represent original communities, paleoecologists seek comparisons between death assemblages and their source communities. These comparisons have traditionally used nearshore, marine invertebrate assemblages for their logistical ease, high abundance, and comparable census data from living communities. For large marine vertebrates, like cetaceans, measuring their diversity in ocean ecosystems is difficult and expensive. Cetaceans, however, often beach or strand themselves along the coast, and archived data on stranded cetaceans have been recorded, in some areas, over several decades. If the stranding record is interpreted as a death assemblage, then the stranding record may represent a viable alternative for measuring diversity in living communities on directly adjacent coastlines. This study assessed the fidelity of the cetacean stranding record in the eastern North Pacific Ocean. The living community in this region has been studied for over 100 years and, recently, extensive and systematic live transect surveys using ship-based observing platforms have produced a valuable source of live diversity data. Over this same period, the U.S. Marine Mammal Stranding Program has collected and archived a record of cetacean strandings along the U.S. Pacific coastline, providing an ideal death assemblage for comparison. Using fidelity metrics commonly used in marine invertebrate taphonomy, I determined that the stranding record samples the living cetacean community with high fidelity, across fine and coarse taxonomic ranks, and at large geographic scales (.1000 km of coastline). The stranding record is also richer than the live surveys, with live-dead ratios between 1.1 and 1.3. The stranding record recovers similar rank-order relative abundances as live surveys, with statistical significance. Also, I applied sample-based rarefaction methods to generate collector's curves for strandings along the U.S. Pacific Coast to better evaluate the spatiotemporal characteristics of the stranding record. Results indicate that saturation (i.e., sampling .95% assemblage) at species, genus, and family levels occurs in less than five years of sampling, with families accumulating faster than species, and larger geographic regions (i.e., longer coastlines) accumulating taxa the most rapidly. The high fidelity of the stranding record, measured both in richness and by ranked relative abundance, implies that ecological structure from living cetacean communities is recorded in the death assemblage, a finding that parallels marine invertebrate assemblages, though at far larger spatial scales. These results have implications for studying cetacean ecology in both modern and ancient environments: first, these results imply that the stranding record, over sufficiently long time intervals, yields a richer assemblage than using linetransect methods, and faithfully records aspects of community structure; and second, these results imply that geochronologically well-constrained fossil cetacean assemblages ...

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“…In part, this is due to the lack of long-term data sets that span a sufficient range of climatic variations. The structure of marine ecosystems changes at various temporal scales through seasonal, annual and decadal fluctuations (Hawkins et al 2003, Evans et al 2005, and in response to catastrophic events that may alter food chains (Trillmich & Ono 1991, Ward et al 2001. A means of detecting subtle ecosystem changes is through monitoring foraging parameters of apex predators, such as pinnipeds (Hindell et al 2003).…”

Section: Introductionmentioning

confidence: 99%

“…On a longer time scale, the ACW pulses colder than average, then warmer than average Antarctic waters in a northerly direction in a 4 to 5 yr cycle (White & Peterson 1996). Also, the ACW influences a near-decadal cycle in zonal (westerly) and meridional (southerly) winds, and this cycle has been linked to variability in fish recruitment patterns (Thresher 1994) and cetacean stranding periodicity in southeastern Australia (Evans et al 2005). Further oceanographic investigations in the Bass Strait region are required to help clarify the way in which currents and meteorological conditions may influence sea temperatures.…”

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confidence: 99%

Sea temperature variations mediate annual changes in the diet of Australian fur seals in Bass Strait

Kirkwood¹,

Hume²,

Hindell³

2008

Mar. Ecol. Prog. Ser.

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Using a 9-yr data set, we investigated annual fluctuations in the diet of an apex predator, the Australian fur seal Arctocephalus pusillus doriferus. At Seal Rocks (northern Bass Strait), home to 25% of the entire species population, we assessed diet through collections (1997 to 2006) of scat and regurgitate samples. We identified prey remains of 42 fish taxa and 7 cephalopod taxa. Only crustaceans that were fish parasites or fish prey (amphipods and isopods) were found; no birds were identified in the samples. Six species represented 80% (as frequency of occurrence) of the fish prey, and the arrow squid Nototodarus gouldi represented 70% of cephalopod prey. There was significant annual variability in the diet. Principal component analysis indicated this was variability due to the presence of redbait Emmelichthys nitidus in some years, and its near absence and replacement in other years by increased proportions of barracouta Thyrsites atun, red cod Pseudophycis bachus and leatherjackets (Family Triglidae). Generalised Linear Models indicated the annual variation was related to mean sea surface temperatures in western Bass Strait where the seals foraged. Redbait proliferated in cooler years and were less abundant in warmer years. No corresponding annual correlation was evident between the prey assemblages and either annual fisheries catch-per-unit-effort or the annual mean Southern Oscillation Index. The propensity for diet regimes to persist for several years, then change suggests that oceanographic fluctuations probably influence previously unrecognised multi-year cyclic fluctuations of prey and of Bass Strait ecosystems. KEY WORDS: Arctocephalus · Fur seal diet · Sea temperature · Bass strait · Emmelicthys nitidus Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 369: [297][298][299][300][301][302][303][304][305][306][307][308][309] 2008 Arnould & Kirkwood 2008). Like other fur seals, such as the New Zealand fur seal A. forsteri (Harcourt et al. 2002), Australian fur seals are generalist predators and consume a range of benthic and pelagic prey; they exhibit some spatial and temporal variations in diet. During the 1920s and 1940s, their diet at breeding colonies in northern Bass Strait was determined by inspection of stomach contents in several shot animals, and comprised mainly barracouta (also known as snoek Thyrsites atun), cephalopods, and southern rock lobster Jasus novaehollandiae (Lewis 1930, McNally & Lynch 1954. In the 1980s and 1990s, the diet, determined from prey hard parts in scats and regurgitates at sites in southern Bass Strait and south of Tasmania, comprised mainly redbait Emmelichthys nitidus, jack mackerel Trachurus declivis, leatherjackets (Family Monocanthidae) and arrow squid Nototodarus gouldi (Gales et al. 1993, Gales & Pemberton 1994, Hume et al. 2004. Between 1997 and 2001 in northeastern Bass Strait, the same prey, plus red cod Pseudophycis bachus were the key species (Littnan 2003, Littnan et al. 2007; during 2001/2002 in ...

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Periodic variability in cetacean strandings: links to large-scale climate events

Cited by 117 publications

References 15 publications

The high fidelity of the cetacean stranding record: insights into measuring diversity by integrating taphonomy and macroecology

The high fidelity of the cetacean stranding record: insights into measuring diversity by integrating taphonomy and macroecology

Carcasses on the coastline: measuring the ecological fidelity of the cetacean stranding record in the eastern North Pacific Ocean

Sea temperature variations mediate annual changes in the diet of Australian fur seals in Bass Strait

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