Temperature anomaly in western Bass Strait

Blackman, Deane R.; Hinwood, Jonathan Barry; Lleonart, Geoffrey T.

doi:10.1071/mf9870191

Cited by 9 publications

(7 citation statements)

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“…Firstly, the onset of El Niño conditions tends to reduce winter-time circulation along Australia's southern shelf region without there being a compensatory increase in summer currents during El Niño summers , Middleton & Bye 2007. The reduced circulation appears to enhance 304 (Blackman et al 1987). 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).…”

Section: Oceanographic Influencesmentioning

confidence: 99%

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The Leeuwin Current moves southwards along the coast of Western Australia and feeds into the SAC (Kidson & Renwick 2002). Sea temperature anomalies in Bass Strait may also be influenced by the Antarctic Circumpolar Wave (ACW) (which pulses colder then warmer waters northwards from the Southern Ocean in a 4 to 5 yr cycle, White & Peterson 1996), or by meteorological influences (Blackman et al 1987).In this study we aimed to (1) quantify the interannual changes in Australian fur seal diet at the Seal Rocks colony in northern Bass Strait through a 9 yr program of scat sampling, (2) relate the variations in prey assemblages to broad scale oceanographic variables, and (3) assess the ecological implications of these relationships for variability in southeastern Australian marine ecosystems. …”

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“…Water bodies that may enter the strait are the Subantarctic Surface Water (SASW) from the south, South Australian Current (SAC) from the northwest and East Australian Current (EAC) from the northeast (Newell 1961). Most current flow is eastward and enhanced by the predominantly westerly winds across southern Australia (Blackman et al 1987, Middleton & Bye 2007.Inter-annual variability in Bass Strait water temperature and productivity may be influenced by broad-scale events, including the ENSO in the western Pacific Ocean (Kidson & Renwick 2002, Middleton & Bye 2007. ENSO cycles influence the relative strength of the Leeuwin Current, causing variability in ocean productivity and species' movements (Pearce & Phillips 1988, Wilson et al 2001.…”

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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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Section: Oceanographic Influencesmentioning

confidence: 99%