Abstract
The growth and reproductive biology of the limpet Patella aspera were studied in the north-eastern Atlantic, Madeira archipelago, to enhance the knowledge concerning biological parameters and population dynamics of this species. This study comprised the estimation of growth rates, sexual maturity, reproduction, recruitment patterns, mortality coefficients and the exploitation rate, and yield-per-recruit (Y/R) based on monthly shell-length frequency data. A total of 16,941 specimens were sampled from January to December 2015. The relative growth pattern exhibited a negative allometric nature of growth for both sexes. The estimated von Bertalanffy growth parameters showed an asymptotic length of 84.15 mm for females and 80.51 mm for males with a growth coefficient of 0.36 and 0.32 year−1 respectively. P. aspera in this geographical area is a moderately long-lived limpet with a predominance of specimens younger than 3 years old. This species is a winter breeder with a reproductive cycle encompassing three main periods namely development, spawning and resting with a synchronous gametogenesis for both sexes. Gonadal development lasts from October to December, spawning likely occurs from January until April and resting occurs from May to September. The mean size at sexual maturity was determined as 41.78 mm for females and 38.29 mm for males and the length at first capture as 42.62 mm. The recruitment pattern was continuous throughout the year with a major peak identified in March. The natural, fishing and total mortalities were similar between sexes, with fishing mortality exerting greatest pressure on this resource. However, yield-per-recruit analysis showed that the stock of P. aspera, in the study area, is exploited at levels below the fishing mortality that returns maximum sustainable yield. This study revealed that currently the stock of P. aspera is under-exploited, nonetheless due to it’s slow growth and long life, continuous monitoring and the enforcement of the existing harvest regulations must be accomplished if future over-exploitation is to be avoided. Further genetic studies are necessary to establish connectivity of the populations and improve present conservation strategies.
Highlights
Limpets are marine gastropods that inhabit the rocky shores
The relative growth coefficient obtained for P. aspera was significantly lower than 3 for both sexes suggesting that this species growth has a negative allometric nature supported by high values of correlation indicating an elevated predictability between shell length and weight for this species
The b values obtained for females and males of P. aspera in the Madeira archipelago were in accordance with the range of values usually encountered for this parameter in marine species, which lies between 2.5 and 3.5 [19, 39]
Summary
Limpets are marine gastropods that inhabit the rocky shores. These species play an important role in regulating the ecological balance of their habitat and have often been used as biological indicators in evaluating the consequences of anthropogenic impact on this ecosystem [1, 2].Patella aspera Röding, 1798 is one of the fourteen worldwide recognized species of the genus Patella Linnaeus, 1758. Limpets are marine gastropods that inhabit the rocky shores. These species play an important role in regulating the ecological balance of their habitat and have often been used as biological indicators in evaluating the consequences of anthropogenic impact on this ecosystem [1, 2]. Patella aspera Röding, 1798 is one of the fourteen worldwide recognized species of the genus Patella Linnaeus, 1758. This species is endemic to the Macaronesian archipelagos, where it is highly exploited for human consumption [3], and occurs in Madeira archipelago together with Patella candei d’ Orbigny, 1840 and Patella piperata Gould, 1846.
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