Seasonal occurrence and distribution of Bryde's whales in the Hauraki Gulf, New Zealand

Abstract

The Hauraki Gulf is a large, shallow embayment located north of Auckland City (36°51′S, 174°46′E), New Zealand. Bryde's whales (Balaenoptera edeni) are the most frequently observed balaenopterid in these waters. To assess the use of the Hauraki Gulf for this species, we examined the occurrence and distribution in relation to environmental parameters. Data were collected from a platform of opportunity during 674 daily surveys between March 2003 and February 2006. A total of 760 observations of Bryde's whales were recorded throughout the study period during 371 surveys. The number of Bryde's whales sighted/day was highest in winter, coinciding with the coolest median sea‐surface temperature (14.6°C). Bryde's whales were recorded throughout the Hauraki Gulf in water depths ranging from 12.1–59.8 m (mean = 42.3, SD = 5.1). Cow–calf pairs were most frequently observed during the austral autumn in water depths of 29.9–53.9 m (mean = 40.8, SD = 5.2). Data from this study suggest Bryde's whales in the Hauraki Gulf exhibit a mix of both “inshore” and “offshore” characteristics from the Bryde's whales examined off the coast of South Africa.

Local abundance, apparent survival and site fidelity of Bryde’s whales in the Hauraki Gulf (New Zealand) inferred from long-term photo-identification

“…In the Hauraki Gulf, it appears that there is a higher occurrence of whales during the austral winter (Wiseman et al 2011), although seasonality was not detected in a more recent study (Dwyer 2014). Bryde's whales in the Hauraki Gulf are subject to a high level of anthropogenic mortality, as evidenced by records of ship strikes and entanglements (Stockin et al 2008, Wiseman 2008, Riekkola 2013, Constantine et al 2015.…”

“…Daily surveys typically lasted 5 h following a non-system-atic survey route primarily determined by the prevailing weather conditions (further details in Wiseman et al 2011).…”

“…In New Zealand, Bryde's whales are reported only for the north-eastern coast of the North Island (Baker & Madon 2007, Wiseman 2008) and occur year-round in the Hauraki Gulf (Behrens & Constantine 2008, Wiseman et al 2011). The whales have been ob served throughout the inner Gulf in water depths ranging from 12 to 60 m (Wiseman et al 2011).…”

“…The whales have been ob served throughout the inner Gulf in water depths ranging from 12 to 60 m (Wiseman et al 2011). Some whales have been resighted regularly over multiple years, including reproductive females accompanied by their calves (Wiseman 2008).…”

Attack on blue penguin by a New Zealand fur seal

“…This region is highly productive because of the influence of the East Auckland Current, which supports a variety of marine mammal (e.g. Stockin et al 2008;Wiseman et al 2011) and bird (e.g. Taylor and Tennyson 1999;Pierre & Norden 2006) species.…”