Southern Right Whale (Eubalaena australis) Reproductive Success is Influenced by Krill (Euphausia superba) Density and Climate

Abstract

The reproductive success of southern right whale (Eubalaena australis) depends on body condition and, therefore, on foraging success. This, in turn, might be affected by climatically driven change in the abundance of the species main prey, krill (Euphausia superba), on the feeding grounds. Annual data on southern right whale number of calves were obtained from aerial surveys carried out between 1997 and 2013 in southern Brazil, where the species concentrate during their breeding season. The number of calves recorded each year varied from 7 to 43 ( = 21.11 ± 11.88). Using cross-correlation analysis we examined the response of the species to climate anomalies and krill densities. Significant correlations were found with krill densities (r = 0.69, p = 0.002, lag 0 years), Oceanic Niño Index (r = −0.65, p = 0.03, lag 6 years), Antarctic Oscillation (r = 0.76, p = 0.01, lag 7 years) and Antarctic sea ice area (r = −0.68, p = 0.002, lag 0 years). Our results suggest that global climate indices influence southern right whale breeding success in southern Brazil by determining variation in food (krill) availability for the species. Therefore, increased frequency of years with reduced krill abundance, due to global warming, is likely to reduce the current rate of recovery of southern right whales from historical overexploitation.

Future recovery of baleen whales is imperiled by climate change

“…Whale species predominantly feeding in mid‐latitudes (40–60°S), such as humpback, fin and southern right whales, were more heavily impacted than those distributed further south because of predicted declines in krill and copepod prey in mid‐latitudes. This highlight that areas around the Antarctic circumpolar current are highly vulnerable to climate‐driven changes (Hill, Murphy, Reid, Trathan, & Constable, ), and supports recent evidence of the direct cause–effect of the climate–krill–whale relationship for southern right whales (Seyboth et al, ).…”

“…However, the exact mechanisms of change are still unclear as little is known of the dynamics among interacting species in Antarctic ecosystems. Recent research shows that global climate indices influence southern right whale breeding success by determining variation in food (krill) availability (Seyboth et al, ). Changes in predator populations in response to climate‐induced changes in their environment and/or prey have been observed for other species in the Southern Hemisphere.…”

Aerial surveys for Antarctic minke whales (Balaenoptera bonaerensis) reveal sea ice dependent distribution patterns

“…However, low encounter rates may also be related to the absence of ice in the area covered by our surveys, located further north around the tip of the Antarctic Peninsula compared to the other studies. Overall winter sea-ice extent has recently been suggested to directly affect the body condition of krill predators after the feeding seasons (Bengtson Nash et al, 2017;Braithwaite, Meeuwig, Letessier, Jenner, & Brierley, 2015;Seyboth et al, 2016). Observations from the Bellingshausen and Amundsen Sea have shown that more AMWs were observed in years with more ice compared to years with less ice along the Antarctic Peninsula (Kasamatsu, Ensor, Joyce, & Kimura, 2000;Thiele et al, 2004).…”

Signals from the south; humpback whales carry messages of Antarctic sea‐ice ecosystem variability

“…Whilst a baseline isotopic change (i.e. reported for other baleen whale krill consumers (Braithwaite, Meeuwig, Letessier, Jenner, & Brierley, 2017;Leaper et al, 2006;Seyboth et al, 2015). This is the first time, however, that nonlethal, chemical and biochemical biomarkers of the core sentinel parameters of diet and adiposity have been targeted.…”