Weight–length relationships of four intertidal mollusc species from the northeastern Atlantic Ocean and their potential for conservation

ABSTRACT

Weight-length relationships (WLRs) are frequently used for the development of comparative studies of life history, population dynamics, ecosystem modelling and estimation of the production and biomass of populations among regions. WLRs provide information about growth, wellbeing and fitness of a population in a marine environment. WLRs for four topshells (Phorcus atratus, Phorcus lineatus, Phorcus mariae, Phorcus sauciatus) caught in North-eastern Atlantic Ocean (Azores, Canaries, Cape Verde, Madeira and Mainland Portugal) were established and their relative growth was assessed. The results showed that almost all species exhibited a positive allometric growth. A comparative study on the effect of harvest in the relative growth of P. sauciatus in the archipelago of Madeira showed that all the populations from exploited areas exhibited a negative allometric growth in contrast to the populations from the Marine Protected Areas (MPAs) which were predominantly isometric. The present results indicate that the conservation measures established in the protected areas promoted a positive effect in the protected populations and are valuable for establishing a set of monitoring and management measures aiming at the sustainable exploitation and conservation of these species. These results are important to demonstrate the role of MPAs in the conservation of these keystone species in the north eastern Atlantic Ocean rocky shore ecosystems.

KEYWORDS:

• Relative growth
• topshells
• MPAs
• north-eastern Atlantic Ocean

Acknowledgements

We are grateful to the Direção de Serviços de Monitorização, Estudos e Investigação do Mar (DSEIMar) of the Regional Directorate of the Sea of the Autonomous Region of Madeira. We acknowledge Dr.ª Antonieta Amorim for providing the maps used in this work and are also grateful to André Pinto and Jorge Lucas for their help during this work, namely in biological sampling and harvesting surveys. We also show our appreciation to Drª Carolina Santos and the IFCN (Instituto das Florestas e Conservação da Natureza da RAM) for allowing and collaborating in the collection of topshells in the natural reserve zones.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The first author (RS) was supported by a grant from ARDITI/OOM/2016/010 (M1420-01-0145-FEDER-000001-Observatório Oceânico da Madeira-OOM) and the third (RR) partially funded by UCSC (FAA 01/2020). The present study was also supported by the UE European Regional Development Fund in the framework of the Projects MARISCOMAC (MAC/2.3d/097) and MACAROFOOD (MAC/2.3d/015), and the Regional Government of Madeira and by the strategic project UID/MAR/04292/2019 granted to MARE by FCT.