Multi Year Observations Reveal Variability in Residence of a Tropical Demersal Fish, Lethrinus nebulosus: Implications for Spatial Management

Abstract

Off the Ningaloo coast of North West Western Australia, Spangled Emperor Lethrinus nebulosus are among the most highly targeted recreational fish species. The Ningaloo Reef Marine Park comprises an area of 4,566 km2 of which 34% is protected from fishing by 18 no-take sanctuary zones ranging in size from 0.08–44.8 km2. To better understand Spangled Emperor movements and the adequacy of sanctuary zones within the Ningaloo Reef Marine Park for this species, 84 Spangled Emperor of a broad spectrum of maturity and sex were tagged using internal acoustic tags in a range of lagoon and reef slope habitats both inside and adjacent to the Mangrove Bay Sanctuary zone. Kernel Utilisation Distribution (KUD) was calculated for 39 resident individuals that were detected for more than 30 days. There was no relationship with fish size and movement or site fidelity. Average home range (95% KUD) for residents was 8.5±0.5 km2 compared to average sanctuary zone size of 30 km2. Calculated home range was stable over time resulting in resident animals tagged inside the sanctuary zone spending ∼80% of time within the sanctuary boundaries. The number of fish remaining within the array of receivers declined steadily over time and after one year more than 60% of tagged fish had moved outside the sanctuary zone and also beyond the 28 km2 array of receivers. Long term monitoring identified the importance of shifting home range and was essential for understanding overall residency within protected areas and also for identifying spawning related movements. This study indicates that despite exhibiting stable and small home ranges over periods of one to two years, more than half the population of spangled emperor move at scales greater than average sanctuary size within the Ningaloo Reef Marine Park.

Migration and movement profiles of a potadromous fish (Brachymystax lenok Pallas 1773) in a highly connected river system (Mongolia)

“…Kernel densities (KD) were used to depict the probability of an individual occurring at a location within its home range as a function of the relocation points (receiver detection days) (Pillans et al, 2014;White & Garrott, 1990). A normal KD function with a bandwidth of 0.75 km was used to calculate the 50% and 95% KD for those fish that had been detected on >15 days during the study period and on >2 receivers (Duong, 2017;Vokoun, 2003;Worton, 1989).…”

Quantifying the conservation value of seascape connectivity: a global synthesis

“…At present, little is known about how the characteristics of seascapes at reserve boundaries (i.e. whether habitat is continuous or patchy) influence movement and dispersal from reserves (Freeman et al ., ; Pillans et al ., ; Pittman et al ., ). Spillover, which is a fisheries objective for many reserves (Halpern et al ., ), will likely be enhanced where habitat is continuous at reserve boundaries, but this will also work against the accumulation of fish biomass in reserves, which is a key conservation objective (Babcock et al ., ; Edgar et al ., ).…”

Assessing environmental correlates of fish movement on a coral reef

“…Cooler temperatures were recorded in winter during the middle of the year, while warmer temperatures occurred in summer towards the end and beginning of each year. Neither season nor month could be incorporated as fixed factors into the models because the presence of fish from each of the three deployments was influenced by time since deployment (which is not uncommon; Pillans et al 2014), so these factors were incorporated as random effects. Despite this bias, individuals were detected on the monitored reef slope in all months of the year, at all temperatures, regardless of season.…”

“…The opposite trend in atmospheric pressure to water temperature occurred on a weekly and monthly (seasonal) timescale, so it is uncertain whether daily absence of fish could be associated with days of lower atmospheric pressure. Declines in atmospheric pressure during extreme storm events has caused movements of sharks (Heupel et al 2003;Udyawer et al 2013), and was thought to be responsible for the movement of individuals away from detection range for the congener Lethrinus nebulosus (Pillans et al 2014) and flounder P. dentatus (Henderson et al 2014). However, no tropical cyclone was encountered during the monitoring period of this study, and previous movements in response to extreme weather were assumed to be associated with water temperature (Tobin et al 2010).…”

“…Only recently has research investigated the spatial ecology of emperors and identified movement patterns among species and individuals that may be related to changes in environmental conditions (Taylor and Mills 2013;Currey et al 2014a;Pillans et al 2014). The aim of this study was to identify which environmental variables explained the movement patterns of lethrinids at the reef scale, by assessing whether the presence and vertical space use of adult L. miniatus along reef slopes was related to water temperature, air pressure, wind speed, wind direction, rainfall, or moon phase.…”