Local densities and habitat preference of the critically endangered spotted handfish (Brachionichthys hirsutus): Large scale field trial of GPS parameterised underwater visual census and diver attached camera

Abstract

The critically endangered spotted handfish (Brachionichthys hirsutus) is restricted to a limited number of locations in south-eastern Tasmania, Australia. As is often the case for rare species, conducting statistically adequate surveys for B. hirsutus can be costly and time consuming due to the low probability of encountering individuals. For the first time we used a highly efficient and rigorous Global Positioning System (GPS) parameterised underwater visual census (GUVC) to survey B. hirsutus abundance within all nine known local populations in the Derwent Estuary within one season. In addition, a benthic microhabitat assessment was conducted simultaneously using a GoPro® camera attached to diver to determine B. hirsutus microhabitat preferences. B. hirsutus local populations varied between sites, with densities ranging from 1.58 to 43.0 fishes per hectare. B. hirsutus demonstrates a strong preference for complex microhabitat features, such as depressions and ripple formations filled with biogenic substrates (e.g. shells) but avoids simple, low relief microhabitats (e.g. sand flats) and areas dominated by ephemeral, filamentous algae. Complex microhabitats may enable B. hirsutus to avoid predators, increase forage opportunities or provide higher quality spawning sites. This first wide-scale application of GUVC for B. hirsutus allowed us to survey a larger number of sites than previously possible to provide a robust reference point for future long-term monitoring.

Genetic diversity and restricted genetic connectivity in an endangered marine fish (

“…Restricted movement, even among locations is suggested, with reproduction and replenishment of locations being reliant mostly on recruitment within locations. This direct recruitment (Bruce et al 1998) and micro-habitat preference (Wong et al 2018) characteristic of spotted handfish, alongside anthropogenic impacts, may have contributed to this once 'common' species in south-eastern Tasmanian waters (Last and Gledhill 2009) now present as fragmented populations. Importantly, this lack of movement between fragmented populations may be relevant for other species of handfish, including T. politus, which is known from only two small locations, and B. ziebelli, which has not been sighted since ,2005, as well as other data-deficient species .…”

“…The spotted handfish is a small (individuals grow up to ,135 mm; Bessell 2018), rare and cryptic species found in the cool, temperate coastal marine waters in Tasmania (Bruce et al 1998;Lynch et al 2015;Wong et al 2018). Between the 1980s and 1990s, spotted handfish experienced significant population declines (Barrett 1996), resulting in the species being the first marine fish to be listed as Critically Endangered under the Australian Environment Protection and Biodiversity Conservation Act (1999); it is also listed as Endangered in Tasmania (under the Threatened Species Protection Act 1995) and as Critically Endangered by IUCN (Bruce and Last 1996).…”

“…These hotspots are the only known locations of spotted handfish populations (as at 2021, following extensive surveys, by the authors T. Lynch and M. Green, National Handfish Recovery Team (NHRT) divers and consultants undertaking environmental impact assessments). In these areas, spotted handfish are habitat specialists that live on soft sediments, at depths from 1 to 60 m (Last and Gledhill 2009), with the location of the hotspots likely being a result of particular micro-habitat features for which spotted handfish shows a strong preference (Lynch et al 2015;Wong et al 2018).…”

Distribution patterns and habitat associations ofSandelia bainsii(Teleostei:Anabantidae), a highly threatened narrow‐range endemic freshwater fish

“…The lack of specific habitat and abundance relationship is likely to be the main reason that has facilitated persistence of this species in a highly altered landscape in the Kat River catchment. In general, several studies have reported that endangered fishes often exhibit clear habitat requirements for different aspects of their life history, including feeding, refuge and spawning (Knaepkens et al ., 2004; Olden et al ., 2010; Wong et al ., 2018). Although the loss of critical habitats for endangered species often leads to both range reduction and decline in population sizes (Januchowski‐Hartley et al ., 2016; Lintermans, 2013), these species usually exhibit clear habitat affinities, which are often identifiable and prioritised for conservation to mitigate further losses.…”

Detection of protection benefits for predatory fishes depends on census methodology

“…As a result, many attempts have been made to adapt the methodologies to maximize species detectability, by increasing the number of observers (Issaris et al, 2012; Bernard et al, 2013), sampling replicates (MacNeil et al, 2008), or varying the size of the transects (Harmelin‐Vivien et al, 2015; Prato et al, 2017). Also, sampling techniques have been further developed in order to increase the accuracy of data (Katsanevakis et al, 2012), such as the combination of UVCs with mark and recapture methods (Hackradt, 2012), repeated presence–absence surveys for occupancy models (Issaris et al, 2012), removal methods (Söffker et al, 2015), distance sampling (Kulbicki & Sarramégna, 1999; Irigoyen et al, 2018), and Global Positioning System (GPS)‐tracked roaming transects (Beck et al, 2014; Lynch, Green & Davies, 2015; Irigoyen et al, 2018; Wong et al, 2018). Among them, GPS‐tracked roaming transects increase the efficiency of UVCs by covering 33–75% more area than CSTs for a comparable diving time (Beck et al, 2014; Lynch, Green & Davies, 2015; Irigoyen et al, 2018), thus allowing the sampling of very sparse populations that might otherwise require much more effort to get a record, and may even remain undetected.…”