Seascape ecology, the marine-centric counterpart to landscape ecology, is rapidly emerging as an interdisciplinary and spatially explicit ecological science with relevance to marine management, biodiversity conservation, and restoration. While important progress in this field has been made in the past decade, there has been no coherent prioritisation of key research questions to help set the future research agenda for seascape ecology. We used a 2-stage modified Delphi method to solicit applied research questions from academic experts in seascape ecology and then asked respondents to identify priority questions across 9 interrelated research themes using 2 rounds of selection. We also invited senior management/conservation practitioners to prioritise the same research questions. Analyses highlighted congruence and discrepancies in perceived priorities for applied research. Themes related to both ecological concepts and management practice, and those identified as priorities include seascape change, seascape connectivity, spatial and temporal scale, ecosystem-based management, and emerging technologies and metrics. Highest-priority questions (upper tercile) received 50% agreement between respondent groups, and lowest priorities (lower tercile) received 58% agreement. Across all 3 priority tiers, 36 of the 55 questions were within a ±10% band of agreement. We present the most important applied research questions as determined by the proportion of votes received. For each theme, we provide a synthesis of the research challenges and the potential role of seascape ecology. These priority questions and themes serve as a roadmap for advancing applied seascape ecology during, and beyond, the UN Decade of Ocean Science for Sustainable Development (2021-2030).

As coastal species experience increasing anthropogenic pressures there is a growing need to characterise the ecological drivers of their abundance and habitat use, and understand how they may respond to changes in their environment. Accordingly, fishery-independent surveys were undertaken to investigate shark abundance along approximately 400 km of the tropical east coast of Australia. Generalised linear models were used to identify ecological drivers of the abundance of immature blacktip Carcharhinus tilstoni/Carcharhinus limbatus, pigeye Carcharhinus amboinensis, and scalloped hammerhead Sphyrna lewini sharks. Results indicated general and species-specific patterns in abundance that were characterised by a range of abiotic and biotic variables. Relationships with turbidity and salinity were similar across multiple species, highlighting the importance of these variables in the functioning of communal shark nurseries. In particular, turbid environments were especially important for all species at typical oceanic salinities. Mangrove proximity, depth, and water temperature were also important; however, their influence varied between species. Ecological drivers may promote spatial diversity in habitat use along environmentally heterogeneous coastlines and may therefore have important implications for population resilience.

The young (neonates, young-of-the-year and juveniles) of many shark species occupy a diverse range of habitats and areas. However, the contribution of individual nurseries or habitats to an adult population is difficult to quantify. In addition, little attention has been paid to the potential importance of 'non-nursery' young shark habitats to the long-term sustainability of shark populations. Portfolio theory predicts that contributions from a diverse range of young shark habitats may reduce variability in the overall production of adults, and maintain population resilience. This review examines case studies of portfolio effects in teleost fish and evaluates the relevance and potential implications of these processes for shark populations. Environmental heterogeneity in young shark habitats can result in locally adapted habitat-use patterns and life history traits. Therefore, young shark habitats may be differentially impacted by anthropogenic disturbance or environmental change, with different habitats performing well at different times. In addition, increased stability in production may be achieved when the effects of localised disturbance in one area are buffered by production in others. However, the behavioural and life history characteristics of some shark species may limit portfolio effects. These include the repeated use of a narrow range of habitats or areas for reproduction, and the production of relatively stable numbers of offspring. This description of the relevance of portfolio theory to shark populations highlights the importance of maintaining habitat diversity. KEY WORDS: Shark · Nursery · Portfolio effect · Population sustainability · Elasmobranch · FisheriesResale or republication not permitted without written consent of the publisher

Effective conservation and management of shark populations is complicated by our limited understanding of their spatial ecology. For example, there are scarce data on diversity in community structure and nursery function across broader geographic scales (e.g. across multiple inshore systems) and the implications of this diversity for shark populations. Accordingly, fishery-independent surveys were undertaken to investigate shark communities along ,400 km of the tropical eastern coast of Australia (18.1-20.68S, 146.0-148.88E). A variety of shark species were encountered, with 19 species of Carcharhiniformes contributing 99.2% of the total shark catch. Of the 1806 sharks captured, 567 were immature, including 336 young-of-the-year individuals. Immature sharks from 18 species were present; however, interspecific variation in the proportions of life-history stages was apparent. Multivariate analyses identified significant spatial heterogeneity in immature-shark communities. Results also highlighted the importance of tropical coastal habitats for numerous shark species, and indicated community-wide spatial structuring of sharks on the basis of body size rather than life-history stage. In addition to building on traditional shark-nursery paradigms, these results demonstrated that data on nursery function from restricted areas may not accurately portray patterns occurring over broader geographic scales, and this diversity may provide population-level benefits for sharks.

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ABSTRACT1. Coastal sharks face increasing pressure from anthropogenic impacts and environmental change. Estimated population declines in some species have created uncertainty about the effectiveness of existing management approaches. In particular, there are scarce data on the benefits of marine protected areas (MPAs) for sharks, including whether they can be used to conserve multiple sympatric species comprising diverse life histories and habitat use patterns.2. This study used fishery-independent longline and gill-net surveys to investigate the effects of sub-bay-sized MPAs (c. 100-300 km 2 ) on the abundance and community structure of tropical coastal sharks. In addition, tag-recapture data from fishery-dependent and fishery-independent sources were used to investigate the movements of individuals across MPA boundaries. 3. Species composition varied significantly between management zones, and overall shark abundance on longlines was higher inside MPAs.4. Length-frequency distributions of blacktip (Carcharhinus tilstoni/Carcharhinus limbatus) and pigeye (Carcharhinus amboinensis) sharks inside MPAs included a greater proportion of sharks larger than c. 800 mm compared with those in open zones, although results varied between gear types for pigeye sharks.5. Tagging and recapture locations indicated repeated and potentially long-term use of MPAs by individuals of some species.6. Although the potential benefits of MPAs were not equal for all species, coastal MPAs may increase the survival of young sharks to maturity, or shelter parts of breeding stocks, and therefore do not necessarily need to be large to provide benefits.

Understanding spatio-temporal patterns in shark occurrence is critical for assessing the ecological role of a species, its vulnerability to human impacts and environmental change, and the efficacy of conservation and management strategies. Investigating these patterns can also develop an understanding of the functioning of coastal shark nurseries. In this context, we undertook a multi-year fisheries-independent survey of shark occurrence along a 400-km stretch of tropical coastline. Logistic regression was used to identify spatial, seasonal and inter-annual variations in the occurrence of neonate and young-of-the-year (YOY) blacktip Carcharhinus limbatus/Carcharhinus tilstoni, pigeye Carcharhinus amboinensis, scalloped hammerhead Sphyrna lewini and spot-tail Carcharhinus sorrah sharks. Results indicated interspecific variations in occurrence. Seasonal variations characterised the occurrence of YOY pigeye, YOY spot-tail and neonate blacktip sharks, whereas spatial variations were more pronounced for YOY blacktip and scalloped hammerhead sharks. These results suggested that the occurrence of young sharks may be more complex than would be predicted by the timing of parturition alone. In addition, spatial heterogeneity in occurrence suggested that proximate bays are likely to vary in terms of the services they provide to young sharks.