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First assessment of distribution and harvesting of common limpet species in the Sinis Peninsula (Sardinia, Italy)

Stefano Marra1, 2*, Stefania Coppa2, Andrea Camedda2, Giorgio Massaro3 and Giuseppe A. De Lucia2
  • 1 Università della Tuscia, Italy
  • 2 CNR-IAMC (Consiglio Nazionale delle Ricerche- Istituto per l'Ambiente Marino Costiero), Italy
  • 3 Area Marina Protetta "Penisola del Sinis - Isola di Mal di Ventre", Italy

Limpets are common benthic molluscs found mainly on the intertidal zone. These organisms are considered keystone species as their grazing activity can shape the characteristics of the intertidal community by limiting the algal coverage in rocks. As demonstrated in different studies, the massive removal of limpets can cause strong community shifts (Boaventura et al., 2002; Jenkins et al., 2005; Borges et al., 2015). In some regions, limpets are collected by humans and their harvesting rate may be so high that it can determine strong reduction in densities. Several studies demonstrated declines in limpet populations as a product of human harvesting (Martins et al., 2008), especially in densely populated areas. In the Sinis Peninsula (Italy, W Mediterranean) the exploitation of limpets, mainly for food purposes, is a common activity. Despite the fact that the area is not yet heavily urbanized and not densely populated, a recent study highlighted how the rate of limpet exploitation is causing the gradual extinction of the local population of the endangered giant limpet Patella ferruginea (Coppa et al., 2015). The case study of the P. ferruginea showed how the overexploitation of limpets is limited mainly by the accessibility of sites, as the higher densities are found in isolated rocks difficult to be reached. Despite this, no data were available yet for the other limpet species. Three other and more common species of limpets are indeed present in the Sinis Peninsula: P. ulyssiponensis, P caerulea and P. rustica. The aim of the present study is to assess the effect of human collection on common limpets by mean of repeated surveys in selected sites spread all along the coastline of the study area. Ten sites were selected including both easily accessible sites (i.e. directly reachable by walk) and hardly accessible ones (i.e. cliff areas that cannot be directly reached from the land). In each site three 2m long fixed transects are being monthly monitored during the period of one year (from June 2015 to September 2016). During surveys, photographic frames of each transect are collected and pictures are subsequently analysed to obtain data of abundance and size of limpets (total shell length, 1mm size class). At the end of the monitoring period, data collected will be analysed with the FISAT II software (FAO-ICLARM stock assessment tools II) to estimate growth curves, mortalities and recruitment patterns of the different species. Here we report the preliminary results on the population structure using data collected in June 2015, August 2015, January 2016 and March 2016. The most common species was P. caerulea, observed in all the monitored transects, followed by P.rustica that was observed in 66% of the transects. On the contrary, specimen of P. ulyssiponensis were present in 26% of the transects with low numbers. The length of the collected specimen ranged from 0.1 cm to 5.3 cm. In easily accessible sites, the length of the biggest specimen observed was 4.8 cm. The total mean number of limpets (number of limpets/m ± standard error) was 104.12 ± 9.75 (June), 79.98 ± 9.01 (August), 85.47 ± 9.69 (January) and 99.18 ± 14.42 (March). In the easily accessible sites the highest mean number recorded (98.31 ± 12.98 in June) was close to the lower level recorded in hardly accessible sites (90.42± 13.65 in August). The highest mean number in hardly accessible sites were recorded in June (112.83 ± 14.98). Small specimen (i.e < 0.6 cm) were detected during each survey, with the higher mean values observed in January (4.4 ± 1.31 limpets/m). Specimen >2cm were more abundant in hardly accessible sites, with the lower numbers detected in January (9.83 ± 2.02 limpets/m) and the higher in June (23.25 ± 3.86 limpets/m). In easily accessible sites specimen >2cm ranged between 11.81 ± 1.66 (June) to 5.78 ± 0.93 limpets/m (January). Furthermore, large specimen (i.e. > 3cm) showed very low numbers in easily accessible sites, with maximum levels observed in June (1 ± 0.28 limpets/m). On the contrary in the hardly accessible sites, levels ranged from 0.88 ± 0.27 (January) to 2.75 ± 0.68 limpets/m (June). This work provide preliminary data on the distribution and exploitation effects on common limpets in the Sinis Peninsula. Results, although preliminary, suggest that the effects of human induced mortality is not negligible with the strongest contraction of abundance observed in August, when human frequentation of the area is higher. Limpets, especially large specimen, are more abundant in hardly accessible sites compared to the easily accessible one. When all data will have been collected at the end of the monitoring period, the analysis of mortality of the different age cohorts in each site will permit to highlight hotspots of human harvesting in the study area providing useful management insight for the conservation of limpets.

References

Jenkins, S.R., Coleman, R.A., Della Santina, P.S., Hawkins, J., Burrows, M.T., Hartnoll, R.G. (2005). Regional scale differences in the determinism of grazing effects in the rocky intertidal. Mar. Ecol. Prog. Ser. 287, 77-86. doi:10.3354/meps287077

Borges, C.D.G., Hawkins, S.J., Doncaster, C.P., Crowe T.P. (2015). Effects of simulated human exploitation of a key grazer, Patella vulgata, on rocky shore assemblages. Mar. Ecol. Prog. Ser. 533, 163-176. doi: 10.3354/meps11356

Boaventura, D., Alexander, M., Della Santina, P., Smith N.D., Ré, P., Cancela da Fonseca, L., Hawkins, S.J. (2002). The effects of grazing on the distribution and composition of low-shore algal communities on the central coast of Portugal and on the southern coast of Britain. J. Exp. Mar. Biol. Ecol. 267, 185-206. doi:10.1016/S0022-0981(01)00372-0

Coppa, S., de Lucia, G.A., Massaro, G., Camedda, A., Marra, S., Magni, P., Perilli, A., Di Bitetto, M., García-Gómez, J.C., Espinosa, F. (2015). Is the establishment of MPAs enough to preserve endangered intertidal species? The case of Patella ferruginea in the Mal di Ventre Island (W Sardinia, Italy). Aquat. Conserv. Mar. Freshw. Ecosys. doi:10.1002/aqc.2579

Martins, G.M, Jenkins, S.R., Hawkins, S.J, Neto, A.I, Thompson, R.C. (2008). Exploitation of rocky intertidal grazers: population status and potential impacts on community structure and functioning. Aquat. Biol. 3, 1-10. doi: 10.3354/ab00072

Keywords: limpets, distribution pattern, population structure, conservation, Human harvesting, Mediterranean

Conference: XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016.

Presentation Type: Poster Presentation

Topic: 1. ECOLOGY, BIODIVERSITY AND VULNERABLE ECOSYSTEMS

Citation: Marra S, Coppa S, Camedda A, Massaro G and De Lucia GA (2016). First assessment of distribution and harvesting of common limpet species in the Sinis Peninsula (Sardinia, Italy). Front. Mar. Sci. Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00148

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Received: 29 Apr 2016; Published Online: 03 Sep 2016.

* Correspondence: Mr. Stefano Marra, Università della Tuscia, Viterbo, Italy, stefano.marra@iamc.cnr.it