Batoid nurseries: definition, use and importance

Abstract

Nursery areas are crucial for many elasmobranch species, providing benefits that increase fitness and survival. Shark nurseries are well studied and our knowledge of their function and importance has expanded over the past few decades. However, little attention has been given to batoid nurseries, with studies covering less than 6% of the 663 currently described species. Threats of extinction faced by batoids reinforce the importance of defining these critical habitats. This review synthesises current knowledge of batoid nursery areas to provide a better understanding of their ecological roles and importance. Historically, different criteria have been used to define viviparous and oviparous batoid nurseries, causing confusion that could lead to failure of conservation and management strategies by under-or overestimating the importance of areas and delaying effective action. We suggest the criteria used to identify shark nurseries be applied to juvenile batoids, standardizing this nursery definition for all elasmobranchs, but we also advocate for a second set of criteria that identifies egg case nurseries. Batoids are thought to play 3 main ecological roles in nursery areas: energetic links, bioturbators and mesopredators. Biotic and abiotic features affect abundance and distribution of batoids within nurseries and likely play a key role in their habitat use. However, analysis of batoid ecological roles in nursery areas is limited by the lack of research on their early life history stages. Thus, identification of areas that support sensitive life stages and an improved understanding of early life history are crucial for the efficient management and conservation of batoid species and their nurseries.

Reproduction and embryonic development of the red stingray Hemitrygon akajei from Ariake Bay, Japan

“…Within a litter, uterine eggs were provisioned with a similar mass of yolk to support initial embryo growth with the exception of four females who had at least one egg more than 0.5 g lighter than the largest egg distribution may be related to habitat preference that accompanies changes in body size and sexual maturity as well as an artefact of sampling methodology. For example, shallower areas including estuaries are used often as a nursery ground and yield predominantly small immature specimens (Martins et al 2018).…”

Research Priorities to Support Effective Manta and Devil Ray Conservation

“…Additionally, juvenile M. thurstoni have been observed in coastal regions of the Gulf of California (Notarbartolo di Sciara, 1988), indicating that protected coastal habitats may be important to juvenile mobulids in general. To date two locations have been identified that meet established criteria for elasmobranch nursery habitats (Heupel et al, 2007;Martins et al, 2018) Figure 3), although other locations are currently undergoing similar assessments. Future work should target locations where juvenile mobulids are known to aggregate or are frequently present, and determine whether these sites meet the criteria for formal classification as a nursery habitat as defined by Heupel et al (2007) and Martins et al (2018).…”

Resource partitioning between two young‐of‐year cownose rays Rhinoptera bonasus and R. brasiliensis within a communal nursery inferred by trophic biomarkers

“…data). Identifying foraging strategies such as resource partitioning in communal nurseries is key for improving spatial conservation and management planning for batoid species (Martins et al, ), especially when the ecological similarity of congeneric species may imply competition and reduced access to food resources that oversimplify food web interactions.…”

“…Elasmobranch nurseries are habitats (commonly shallow protected coastal waters) where juveniles reside to maximise their fitness and survival during this early and high‐risk life history stage (reviewed by Heupel et al, ; Heupel et al , ; Martins et al, ). Of the two strategies proposed for how elasmobranchs utilise a nursery ground ( i.e ., single or multi‐species occupancy), multi‐species occupancy or a communal nursery involves the co‐occurrence of juveniles of more than one species within a defined area (Heupel et al , ; Simpfendorfer & Milward, ).…”

“…To assess the temporal scale of the maternal influence effectively and adopted foraging strategy in the two species, plasma and multiple tissues (fin clip, muscle, liver, red blood cells; RBC) with different turnover rate were analysed. These data will improve knowledge on the use of communal nursery areas by batoids and interspecific resource partitioning strategies adopted by sympatric congeneric species, information which is required for long‐term management (Martins et al, ).…”