Mortality and breeding failure of little penguins, Eudyptula minor, in Victoria, 1995 - 96, following a widespread mortality of pilchard, Sardinops sagax

Abstract

In May 1995, numbers of little penguins, Eudyptula minor, coming ashore declined at Phillip Island and St Kilda concurrently with deaths of many penguins in western Victoria and a massive mortality of one of their food species (pilchard) throughout southern Australia. Among 1926 dead penguins reported were 131 banded birdsrecovered from Phillip Island (86% adults and 14% first-year birds), 26 from Rabbit Island and six from St Kilda. The number of banded penguins found dead per number of adult Phillip Island birds at risk was 2.3% in 1995 compared with an annual mean of 0.7% for 1970–93. Of 29 corpses autopsied, at least 26 died of starvation associated with mild–severe gastro-intestinal parasitism. Following the pilchard mortality, egg-laying by penguins in the subsequent breeding season (1995–96) was ~2 weeks later than the long-term mean and 0.3 chicks were fledged per pair compared with the long-term mean of 1.0. Unlike previous years, few penguins were recorded in Port Phillip Bay in September–October 1995, a period when pilchard schools were infrequently seen. It is concluded that the increase in penguin mortality in northern Bass Strait and the significant reduction in breeding success were associated with the widespread pilchard mortality.

Population biology of infectious diseases shared by wild and farmed fish

“…Those epidemics spread at 10 000 km per year (McCallum et al 2003), causing mass mortality of ϳ30 000 t in Western Australia in 1998-1999 (Gaughan et al 2000) and a 75% decline in pilchard spawning biomass (Ward et al 2001b). Such parasite-induced mass mortality can have cascading ecological effects; the pilchard die-off led to the expansion of competitor species (Ward et al 2001a), reproductive failure in penguins (Eudyptula minor; Dann et al 2000), and diet shifts in gannets (Morus serrator; Bunce and Norman 2000).…”

Contrasting genetic structuring between colonies of the World’s smallest penguin, Eudyptula minor (Aves: Spheniscidae)

“…Some E. minor colonies have undergone declines and even extinction during recorded history (Dann 1992(Dann , 1994Dann et al 2004;Stevenson and Woehler 2007) while others have increased (Dann 1994;Johannesen et al 2003). Known contributors to declines include predation by introduced carnivores (Dann 1992;Overeem andWallis 2003, 2007), mass mortality of important prey species (Dann et al 2000) and an oil spill (Goldsworthy et al 2000). Human settlement has also greatly modified breeding habitat in a few areas via agriculture, housing, recreational activities and coastal erosion (Harris and Bode 1981).…”

Recent growth rate of larval pilchards Sardinops sagax in relation to their stable isotope composition, in an upwelling zone of the East Australian Current

“…Pilchards were not appreciated as being abundant off eastern Australia, until widespread deaths of pilchards were observed in 1995 and again in 1998 (Griffin et al 1997;Gaughan et al 2001). Pilchards are important for the coastal ecosystem, as the effects of this die-off were severe for local marine birds (Bunce and Norman 2000;Dann et al 2000), and for the west coast fishery. Nevertheless, our knowledge of the pilchard on the east coast is very limited, but as the genus is now considered to be monospecific (Grant et al 1998), there are useful parallels with Sardinops studies off Western Australia (Gaughan et al 2001), California (Logerwell and Smith 2001), and Japan (Watanabe and Kuroki 1997).…”