Stock Assessment Framework for Deepwater Sharks in
SIOFA
DELEGATION OF THE EUROPEAN UNION
23 February, 2024
Introduction
The Southern Indian Ocean Fisheries Agreement (SIOFA) plays a
critical role in the conservation and sustainable use of fishery
resources in the high seas of the Southern Indian Ocean.
Challenges
Deepwater shark populations face numerous assessment challenges,
including
- limited data availability and
- unique life-history characteristics.
Necessitating innovative approaches for effective management and
conservation strategies.
Framework Overview
A hierarchical, risk-based assessment framework designed to address
the unique challenges of managing deepwater shark populations.
- Builds upon PSA and moves towards a consideration of Risk
Equivalence and Adaptive Management, i.e.Â
- More uncertainty should not allow greater risk, and as we learn we
adapt.
- Prioritises data collection and analytical methods to provide
actionable conservation measures.
Data Sources
Current Data
- Catch and Effort
- Size Data
- Biological Parameters
Future Data
Innovative data collection methods such as
- Tagging
- Environmental DNA (eDNA) sampling
A better understanding of species distribution and abundance could
help improve
- Spatial and temporal mitigation measues
- Monitoring of stock distribution, abundance and recovery
Spatial and temporal data
Visualising catch weight (or numbers) by year and gear offers
insights into fishing pressure and its spatial distribution, crucial for
identifying areas where management interventions are most needed.
Total catches by gear
Spatial and temporal data
Visualising catch weight (or numbers) by year and gear offers
insights into fishing pressure and its spatial distribution, crucial for
identifying areas where management interventions are most needed.
Total catches by species
Spatial and temporal data
Visualising catch weight (or numbers) by year and gear offers
insights into fishing pressure and its spatial distribution, crucial for
identifying areas where management interventions are most needed.
Catches in 2020 for
Centrophorus Spp
Spatial and temporal data
Visualising catch weight (or numbers) by year and gear offers
insights into fishing pressure and its spatial distribution, crucial for
identifying areas where management interventions are most needed.
Catches by year for
Centrophorus Spp
Size distributions
Large
average size low F v. low average size high F
Centrophorus Sp
Size distributions
Large
average size low F v. low average size high F
Centrophorus granulosus
Size distributions
Centrophorus granulosus
By sex compared to life history traits
Life history traits
Fish Base
What do we have?
Life history traits
Estimates of natural
mortality
Life history traits
Estimation of population
growth rate
Life history traits
Estimates of \(F_{MSY}\)
Hierchical Assessment Framework
The need for flexible management approaches that evolve with new
data
Risk Assessment Framework
The proposed framework underscores the importance of innovative
assessment and management strategies for deepwater sharks in the SIOFA
area. Enabling collaborative effort and targeting of research
Model Validation
Validation of models play a crucial role in science, ensuring that
management decisions are based on reliable and robust scientific
evidence.
Management Measures
Potential measures can be explored, including spatial management and
gear modifications, to mitigate the impact on deepwater shark
populations.
Stakeholder Engagement
Engaging stakeholders in the management process ensures that diverse
perspectives are considered, enhancing the legitimacy and effectiveness
of conservation measures, required as we move towards EAF.
