African Journal of Aquatic Science ISSN: 1608-5914 (Print) 1727-9364 (Online) Journal homepage: https://www.tandfonline.com/loi/taas20 Using action cameras to estimate the abundance and habitat use of threatened fish in clear headwater streams B Hannweg, SM Marr, LE Bloy & OLF Weyl To cite this article: B Hannweg, SM Marr, LE Bloy & OLF Weyl (2020): Using action cameras to estimate the abundance and habitat use of threatened fish in clear headwater streams, African Journal of Aquatic Science, DOI: 10.2989/16085914.2019.1701404 To link to this article: https://doi.org/10.2989/16085914.2019.1701404 View supplementary material Published online: 12 May 2020. Submit your article to this journal Article views: 6 View related articles View Crossmark data Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=taas20 African Journal of Aquatic Science 2020, 45(1): xxx–xxx Copyright © NISC (Pty) Ltd Printed in South Africa — All rights reserved AFRICAN JOURNAL OF AQUATIC SCIENCE This is the final version of the article that is published ISSN 1608-5914 EISSN 1727-9364 ahead of the print and online issue https://doi.org/10.2989/16085914.2019.1701404 Short Note Using action cameras to estimate the abundance and habitat use of threatened fish in clear headwater streams B Hannweg1,2, SM Marr2,3* , LE Bloy1,2,3 and OLF Weyl1,2,3 1 Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, South Africa 2 DSI/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity, Grahamstown, South Africa 3 Centre for Invasion Biology, South African Institute for Aquatic Biodiversity, Grahamstown, South Africa *Correspondence: [email protected] Snorkel and electrofishing surveys are the traditional baseline methods for fish surveys in clear headwater streams. However, action cameras provide a non-harmful alternative to monitor freshwater fish populations to develop informed conservation management initiatives. In this paper, estimates from photographs and videos from action cameras are compared with snorkel survey estimates of the density of a threatened endemic minnow species in a headwater stream, Eastern Cape, South Africa. Photograph-based relative abundances of fish summed over five microhabitats in each pool returned equivalent results to snorkel surveys, whereas the equivalent video-based abundance estimates were approximately 50% greater than the snorkel estimates. Therefore, photograph-derived estimates could be used as an alternative to snorkel surveys for fish population monitoring and habitat use studies in clear headwater streams. Keywords: freshwater fish, MaxN, monitoring, photographs, snorkel surveys, underwater video analysis Supplementary material: available online at https://doi.org/10.2989/16085914.2019.1701404 Freshwater fish are currently more impacted by human physiological stress, spinal injuries and even internal activities than are other faunal groups (Duncan and haemorrhaging (Snyder 2003). As a result, visual methods, Lockwood 2001; Limburg et al. 2011). Threats, which such as snorkel surveys (Dolloff et al. 1996), and more include habitat degradation/fragmentation, water pollution, recently action cameras, are the preferred survey methods over-abstraction, and the introduction of non-native fish for fish population assessments (Ebner and Morgan 2013), species (Cowx 2002), are compounded for species isolated and studies of ecology, behaviour and habitat utilisation within headwater streams or with restricted geographical (Ebner et al. 2014), particularly for imperilled fish (Ebner et distributions (Ellender et al. 2017). The reason is that al. 2009) these small isolated populations are more vulnerable to In South Africa’s Cape Fold Ecoregion (CFE), sensu (Abell extirpation and local extinctions than more widespread et al. 2008), the imperilled conservation status of many species. Knowledge of the distribution, behaviour and headwater stream fish (Ellender et al. 2017) requires lower abundance of fish, particularly those of conservation risk methods of assessing their abundance, distribution concern, is important for evaluations of their conservation and habitat use (Ellender et al. 2012). Althoug underwater status (Balian et al. 2008; Darwall et al. 2011) and to video analysis (UWVA) provides a useful alternative to develop and direct conservation initiatives (Darwall et al. snorkel surveys and electrofishing, abundance estimates 2008; Darwall et al. 2011). are limited by the camera’s field of view and are, therefore, Fish populations in headwater streams have traditionally generally reported as relative abundance estimates (Ellender been monitored using electrofishing (Hickey and Closs et al. 2012). In addition, post-survey analysis of videos can 2006), seine netting (Anderson et al. 1995; Jordan et be prohibitively time consuming (Cappo et al. 2003; Ebner al. 2008), minnow traps (Kadye and Booth 2014) and et al. 2009). In an attempt to improve UWVA methods, we snorkel surveys (Jordan et al. 2008; Ebner et al. 2009). used headwater stream populations of Eastern Cape redfin Electrofishing, seine netting and trapping involve physically Pseudobarbus afer (Peters, 1864) in the Swartkops River handling fish and could result in post-release mortality as a model system to: (1) compare different non-harmful by increasing the risk of infection through the removal of methods of estimating freshwater fish abundance; (2) assess their protective mucilaginous layer (Brydges et al. 2009), the utility of a 5–camera array to derive absolute abundance whereas electrofishing could result in bleeding at the gills, estimates; and (3) use UWVA to assess habitat use of African Journal of Aquatic Science is co-published by NISC (Pty) Ltd and Informa UK Limited (trading as Taylor & Francis Group) Published online 12 May 2020 2 Hannweg, Marr, Bloy and Weyl fish in small headwater stream habitats. For the current The absolute abundance of P. afer in each pool was study, snorkel surveys, traditionally used to estimate fish estimated by snorkel surveys using the two-pass method abundance in clear headwater streams were used as the described by (Ellender et al. 2018). After the snorkel survey, standard method to evaluate the performance of UWVA. five GoPro Hero 3+ (GoPro Inc., USA) action cameras, in The current study was conducted during February 2016 waterproof housings mounted on tripods, were deployed, in the Groendal Wilderness Area over ten pools in two each covering one of five microhabitats in each pool: perennial headwater tributaries of the Swartkops River, inflow, outflow, deep middle, woody debris and submerged Eastern Cape, South Africa (Table 1). The Eastern Cape root-wads of riparian ferns. Camera placement ensured redfin, a small endemic cyprinid restricted to the headwaters non-overlapping fields of vision. Following recommendations of the Baakens, Swartkops and Sundays rivers in the by Ellender et al. (2012), cameras were set to film for 18 Eastern Cape (Chakona and Skelton 2017) is classified min (including a 3-min acclimation period) at 60 fps (frames as Endangered in the 2017 IUCN-red-list (Chakona et al. per second) and 720 p (progressive display format), while 2017). The sites were chosen as the relationship between concurrently taking 12-megapixel resolution photographs fish relative abundance estimates from UWVA and absolute every five seconds. abundance estimates from electrofishing had previously been Videos were viewed using Windows Media Player demonstrated there for this species (Ellender et al. 2012). (Microsoft Inc.), photographs using Windows Photo Sites, comprising of different pool habitats, were selected Viewer (Microsoft Inc.), and abundance estimated using on the basis of the presence of the target species P. afer, MaxN (sensu Cappo et al. 2003). The first three minutes suitable water clarity for snorkel surveys (>5 m visibility) of the videos was discarded as acclimation time, and the and UWVA, and being deep enough to snorkel (>0.3 m remaining 15-min sample time divided into 30-s intervals deep); see Ellender et al. (2018). Water physico-chemical for which the MaxN was estimated individually. The parameters (pH, temperature, electrical conductivity and MaxN for the deployment was the maximum number of turbidity) were measured using a HANNA HI98129 combo P. afer individuals viewed in any of the 30 s segments. probe and a HANNA HI 98703 turbidity meter (HANNA Similarly, photographs were viewed in batches of six, Instruments, Inc., United States of America.) Three excluding those from the first three minutes, and the MaxN measurements of each parameter were recorded in each determined, as described for videos. pool and averaged for each site. Physical and environmental To account for differences in pool size, absolute parameters for each site at the time of study are presented in abundances of P. afer were standardised to density Table 1. Flow in the system is episodic (Ellender et al. 2011) estimates by dividing the abundance by pool surface area, and, during the current study, flow was negligible. calculated as the product of the length of the pool and Table 1: Summary of habitat measurements, location and physico-chemical parameters (± standard deviation) for ten pools within two headwater tributaries of the Swartkops River, Eastern Cape, South Africa Mean Water Length Area Conductivity Turbidity Site Pool Location width temperature pH (m) (m2) (µS cm−1) (NTU) (m)