Sampling Summary

  • Sampling Location: Victoria Artisanal Fishing Port (Oct 2023 – Apr 2024).
  • Crab Sampled: Total 1106, Female: 413 and Male: 693.
  • Sex Ratio: Male-to-female sex ratio was 1.7:1.
  • Highest Sampling Rate: November with 330 spanner crabs.
  • Trips Sampled: Nine (9) (10 in 2022/2023).
  • Fishing Activity: Concentrated in the Southeast Mahé Plateau.

 

Spanner Crab Graph
Spanner Crab Graph

 

  • Data Trend: The highest crab landing was 115.6 metrics tons (MT) in 2021.
  • Historical Mean: Rest at 30 metric tons (Fig 1). NOTE: Data was obtained from the Catch Assessment Survey collected by the SFA Fisheries Statistics.

 

Data Collection Methods

 

  • Fishing Gear: Mainly tangle nets or ‘kale’, which are baited circular traps with a diameter of approximately 1 meter (Fig 2A).
  • Fishing Deployment: Deployed using a mainline with multiple baited traps attached to it by a trip line. Two sets of anchors to keep the tangle nets on the seafloor (Fig 2B).
  • Spanner Crabs caught are removed from the ‘kale’ and sorted on ice.

 

 

Length Based Indicator

  • Size Distribution: Remained consistent between the 2 years and sexes, with 20232024 only slightly larger (Fig 3).
  • Largest Male: 14.3 cm compared to 13.9 cm in 20222023.
  • Largest Female: 11.6 cm compared to 10.9 cm in 20222023.
  • Smallest Male: 7.7 cm compared to 7.5 cm in 20222023.
  • Smallest Female: 7 cm compared to 7.1 cm in 20222023.

 

  • The fishery’s size limit of 8 cm was set to ensure juvenile protection, sustainable population growth, and reproduction.
  • Crab sampled above 8 cm (Fig 4) consisted of 97% individuals above the size limit; Female 94% and 99% Male.

 

  • Mean Carapace Length: Female and male crabs sampled in 2023/24 had a size of 9 cm and 10.2 cm compared to 8.8 cm and 10.2 cm in 2022/23 (Fig 5).
  • Male mean size remains the same while females increased by 3%.

 

 

Weight Based Indicator

Body Weight:

  • The total weight of female crabs sampled was 102 kg. The mean weight is 0.25 kg.
  • For male crabs sampled, the total weight was 257 kg. The mean weight of 0.36 kg (Fig 6).

 

 

The SFA Research Department would like to thank the fishers for their cooperation and valuable contribution during the sampling process. This project was funded by the European Union Sectoral Support Programme.