Gaining insights into in situ behaviour of an endangered seahorse using action cameras

Abstract

Observation bias is an Achilles heel of behavioural research, particularly during underwater in situ assessments. The advent of small, affordable underwater action cameras has helped to overcome this problem and were used to investigate the behaviour of the endangered Knysna seahorse (Hippocampus capensis) within a South African residential marina estate during the austral summer. Four GoPro® cameras were deployed over three time periods, October to December 2015, December 2015 to January 2016 and January to March 2016, and at different times of the day (morning, midday, afternoon) to ascertain whether: (1) cameras can be used to investigate seahorse behaviour, (2) seahorse behaviour changes throughout the day, (3) behaviour can be used to assess the impact of an external stressor (boat noise) on H. capensis. Thirty‐six hours from a total of 161 h (23%) recorded contained seahorse footage. Seahorses were significantly more visible during the morning and spent >80% of their time hunting. Courting behaviour took place exclusively during the morning and aggression was noted between males only. Boat noise increased during the December holiday period and a significant decrease in seahorse visibility, time spent feeding, and courting events were noted during this time. This suggests that noise has an adverse impact on the behaviour of H. capensis. This study confirms the efficacy of using small action cameras in seahorse behavioural research.

Monthly population density and structure patterns of an endangered seahorse Hippocampus capensis: a comparison between natural and artificial habitats

“…and this results in a marked increase in boat use within the canals and the estuary. When exposed to loud noise, H. erectus exhibited physiological, chronic stress responses with reduced mass and body condition (Anderson et al ., ) and it is possible that the increase in boat noise during the summer holiday period played a role in decreased population densities (Claassens & Hodgson, ). Further research on the potential effect of increased noise on H. capensis caused by boat activity is required.…”

Life history and population dynamics of an endangered seahorse (Hippocampus capensis) within an artificial habitat

“…It was also shown from the open population estimates that the probability of resighting marked individuals decreased over time and was particularly low for the months of November–December. Past research found a comparable decrease in H. capensis numbers and sightability during December 2015 (Claassens & Hodgson, 2018b) which was suggested to be owing to an increase in boat noise during the summer holiday period. As this study was focused on a site located within a residential marina estate, regular maintenance activities take place.…”

“…In addition, different sampling approaches can significantly affect recapture rates; for example, recapture rates for H. zosterae increased from 0.47% to 33% by changing the sampling resolution (Masonjones et al, 2019). This study used closed population surveys to allow (Claassens & Hodgson, 2018b) which was suggested to be owing to an increase in boat noise during the summer holiday period. As this study was focused on a site located within a residential marina estate, regular maintenance activities take place.…”

“…The location of all subsequent recaptures during the 14‐month period, during all subsequent surveys, was recorded following the same process. When an animal was resighted, the location was logged as well as the sex of the animal, the time of day as classified in Claassens and Hodgson (2018b) and the season. In addition to the monthly population surveys, 2–3 additional dives were conducted per month to record movement within the study site.…”

Accurate estimation of fish length in single camera photogrammetry with a fiducial marker

“…Harvey et al, 2001, Jaquet, 2006, behavioural studies (e.g. Nguyen et al, 2014, Claassens andHodgson, 2018) and in aquaculture (e.g. Costa et al, 2006).…”