Abstract

This study describes the use of calcein as a chemical tagging methodology to estimate growth rate variation of the stalked barnacle Pollicipes pollicipes, an ecologically important intertidal species and economic resource, in SW Portugal. Calcein tagging had a high success rate (94%) in marking both juvenile and adult barnacles for a period of 2.5 months, providing a valuable method for obtaining reliable data in growth studies of P. pollicipes. Growth rate decreased with barnacle size and was highly variable amongst individuals, particularly in smaller barnacles. No effect of shore level on barnacle growth was detected. Growth rates were higher in smaller juvenile barnacles, peaking at a 1.1-mm monthly increment in rostro-carinal length (RC) for individuals with RC=5 mm, and decreased with barnacle size (monthly growth rates of 0.5 mm for adult barnacles with RC~12.5 mm). Growth rates observed in adults with commercial interest (RC ≥ 18 mm) was < 0.25 mm per month. The advantages of tagging P. pollicipes with calcein were the possibility of mass marking individual barnacles of different size cohorts within a short period (less than 1 day of manipulation); and reduced time of fieldwork, which is very important because this species inhabits very exposed rocky shores.

Highlights

  • Pollicipes pollicipes is a common barnacle species on very exposed intertidal rocky shores from Brittany to Senegal, where it forms dense aggregates of individuals (Barnes 1996)

  • Fluorescent marks were observed in 282 barnacles out of a total of 300 individuals that were collected in the field

  • Most non-marked individuals were juvenile barnacles (n=16, rostro-carinal length (RC)12.5 mm), probably already present in Maximum capitular plate length measurements were highly and positively correlated among each other and with RC (Pearson’s product-moment correlation, r>0.98 and significant at p

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Summary

Introduction

Pollicipes pollicipes is a common barnacle species on very exposed intertidal rocky shores from Brittany to Senegal, where it forms dense aggregates of individuals (Barnes 1996) It is a very important economic resource in Spain and Portugal, and is heavily exploited (Molares and Freire 2003, Jacinto et al 2010). Marking techniques of individuals in these studies include mapping individuals in relation to marks made in adjacent substrata, or using marks such as insect tags glued to the capitulum plates of suitably-sized individuals. These techniques are difficult to apply and maintain on very exposed shores where time to work is limited. Their success might be low and small animals may be very difficult to mark

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