Fig 1.
Survey tracks (black lines) of a) tour and b) research vessels in the inner Hauraki Gulf, New Zealand.
The solid black line indicates the boundary between the inner and outer HG. The white and yellow lines indicate the 30 and 100 m isobaths, respectively. Bathymetry is depicted with darker shades of blue representing deeper waters (reprinted from NIWA under a CC BY license, with permission from NIWA original copyright 2012; [93]). Inset: Location of the Hauraki Gulf and other places referred to in the text in relation to the North Island of New Zealand.
Table 1.
Description of vessels used for non-systematic surveys.
The nature of the survey refers to the opportunistic (where photo-id was not the only focus of surveys) or dedicated (where photo-id was only focus of surveys).
Fig 2.
Nick/notch distinctiveness (ND) categories used to examine adult common dolphin (Delphinus sp.) images in the Hauraki Gulf, New Zealand.
Individuals were classified as: highly distinctive (D1); distinctive (D2), or; non-distinctive (D3) [1, 4]. The relative depth of the largest nick/notch was determined by dividing the depth of the nick/notch (as measured on a photograph) by the total length of the base of the dorsal fin [101].
Fig 3.
Attributes used to determine if an individual adult common dolphin (Delphinus sp.) was a distinctively marked individual (DMI).
Fig 4.
Examples of distinguishable pigmentation patterns for two adult common dolphins (Delphinus sp.) (Dd_0328 and Dd_0953) photographed in the Hauraki Gulf, New Zealand.
Red circles highlight sections of distinctive corresponding pigmentation.
Fig 5.
Distinctively marked individual (DMI) flow chart used to determine whether an individual adult common dolphin (Delphinus sp.) was distinctively marked and could be included in the Hauraki Gulf Common Dolphin Catalogue (HGCDC).
Table 2.
Assessment of the assumptions for Jolly-Seber models MRC including the potential biases that may occur in population parameter estimates and the methods used to account for potential violations.
Abbreviations: Goodness of fit (GOF). This table has been adapted from Parra et al. [59].
Table 3.
Total seasonal photo-identification effort for adult common dolphins (Delphinus sp.) between 2010 and 2013 in the Hauraki Gulf, New Zealand (Individuals identified are the number of unique animals first sighted per season, whereas D1 and D2 represents the number of distinctive animals per category (D1 and D2) sighted and re-sighted per season).
Abbreviations: Hours (h), summer (S), autumn (A), winter (W), and spring (Sp.). Survey duration refers to the total time on the water per survey (including time spent during encounters and searching for dolphins). Encounter duration refers to the total time during photo-id sessions with groups of dolphins. Search duration refers to the total time searching for dolphins where no photo-id sessions occurred.
Table 4.
Top models from QAICc based-averagingfor sightings data of adult common dolphins (Delphinus sp.) photo-identified between January 2010 and December 2013 in the Hauraki Gulf, New Zealand.
Model results are for POPAN data pooled by seasons and excluded the first capture of each individual. Models are shown for highly distinctive (D1) and highly distinctive and distinctive (D1 & D2) individuals. The lowest QAICc value represents the model that has the most support from the data (in bold). Abbreviations: Apparent survival (ø), capture probability (p), probability of entry (β), constant parameter (.), time-varying parameter (t), model likelihood (ML), and number of parameters (NP).
Fig 6.
Seasonal abundance estimates (±CI) for adult (marked and unmarked) common dolphins (Delphinus sp.) between January 2010 and December 2013 in the Hauraki Gulf, New Zealand, obtained using POPAN.
Estimates are given for highly distinctive (D1) and highly distinctive and distinctive (D1 & D2) individuals.