Movement patterns of a Critically Endangered elasmobranch (Dipturus intermedius) in a Marine Protected Area

Abstract

Marine Protected Areas (MPAs) are widely used in marine management, but for mobile species understanding the spatio‐temporal scale of management measures that is required to deliver conservation benefits depends on a detailed knowledge of species’ movements that is often lacking. This is especially the case for species of skate (Rajidae) for which relatively few movement studies have been conducted. In Scotland, the Loch Sunart to the Sound of Jura MPA covering 741 km2 has been designated for the conservation of the Critically Endangered flapper skate (Dipturus intermedius), but fine‐scale movements within this area remain poorly understood. A passive acoustic telemetry study which coupled acoustic tagging of 42 individuals and a static array of 58 receivers was conducted from March 2016 to June 2017. Using acoustic detection time series, angler capture–recapture data and depth time series from archival tags, fine‐scale movements of individuals were investigated. Overall, 33 of the 42 tagged individuals were detected. Residency, site fidelity and transiency were documented. Residency around receivers, lasting from 3 to more than 12 months, was documented in 16 acoustically detected individuals (48%) and all life‐history categories, but was most noticeable among females. Acoustic detections were associated with depth, salinity and season, but there was no evidence that individuals formed close‐knit groups in the areas in which they were detected. Taken together with historical occurrence records of flapper skate, the prevalence and scale of residency documented here suggest that the MPA is sufficiently large to benefit a notable percentage (38 [24–52]%) of skate found in the study area over monthly and seasonal timescales. This result strengthens the case for the use of MPAs to support the conservation of flapper skate and other skate species that display similar movement patterns in areas of high local abundance.

First report of an egg nursery for the Critically Endangered flapper skate Dipturus intermedius (Rajiformes: Rajidae)

“…Given the number of MPAs for flapper skate in Scotland (n = 2), their spatial separation (70+ km shortest straight-line distance over land and sea between the two sites) and their differences in size and the habitat protected, expanding the coverage of protected areas and improving their connectivity should be a priority for future research and recovery of the species. Building on this study and previous work(Thorburn et al, 2021;Lavender et al, 2021a), a key knowledge gap for future research remains establishing the movements of juveniles and the identification of sites for their protection.…”

“…The However, a successful conservation strategy requires protection across all life history stages of a species (Kinney & Simpfendorfer, 2009), particularly strongly K-selected species such as flapper skate (Ellis et al, 2021). Off the west coast of Scotland, flapper skate show high levels of site affinity to particular areas (Neat et al, 2015;Lavender et al, 2021a); therefore if areas containing habitats important for all life history stages (eggs, juveniles and adults) could be identified and protected, this could deliver important conservation benefits for the species. Thus far, an egg nursery or juvenile nursery have not been identified within the Loch Sunart to the Sound of Jura NCMPA which was designated for the presence of adult skate.…”

“…Thus far, an egg nursery or juvenile nursery have not been identified within the Loch Sunart to the Sound of Jura NCMPA which was designated for the presence of adult skate. While flapper skate are capable of making long-range movements (Little, 1995;Lavender et al, 2021a), very heavily pregnant females have also been observed within the Loch Sunart to the Sound of Jura MPA (Benjamins et al, 2021) suggesting that there…”

“…The Loch Sunart to the Sound of Jura Nature Conservation Nature Conservation MPA (NCMPA), covering an area of 741 km 2 , was designated for the protection of the common skate complex in 2016 based on the high level of site attachment documented in adult flapper skate in the area from mark–recapture records and telemetry (Neat et al, 2015). Flapper skate demonstrated high occupancy of the deep water (100–150 m) within the NCMPA (Lavender et al, 2021a) in the summer months with more movement into shallower areas during the winter (Thorburn et al, 2021; Lavender et al, 2021b). A second, smaller (6.05 km 2 ) urgent NCMPA was designated in March 2021 (Red Rocks and Longay urgent NCMPA, Figure 1) 70+ km to the north of Loch Sunart to the Sound of Jura NCMPA following initial reports from scallop divers and recreational divers of high densities of flapper skate egg cases, and subsequent additional dive surveys and a review of drop‐down video (DDV) camera footage collected during previous surveys of the area.…”

“…The Loch Sunart to the Sound of Jura Nature Conservation Nature Conservation MPA (NCMPA), covering an area of 741 km 2 , was designated for the protection of the common skate complex in 2016 based on the high level of site attachment documented in adult flapper skate in the area from mark-recapture records and telemetry (Neat et al, 2015). Flapper skate demonstrated high occupancy of the deep water (100-150 m) within the NCMPA (Lavender et al, 2021a) in the summer months with more movement into shallower areas during the winter (Thorburn et al, 2021;Lavender et al, 2021b). A second, smaller (6.05 km 2 ) urgent NCMPA The split of the species complex into flapper and common blue skate (Iglésias, Toulhoat & Sellos, 2010) has resulted in difficulty in interpreting earlier literature regarding the reproductive biology of the species.…”