Journal of Coastal Development ISSN : 1410 - 5217 Volume 10, Number 2, February 2007 : 89 - 103 Accredited : 23a / Dikti/Kep/ 2004 GROWTH DETERMINATION OF TROPICAL LIMPET Cellana testudinaria (Linnaeus, 1758) LIVING ON THE ROCKY SHORE OF OHOIWAIT, SOUTHEAST MOLUCCAS, INDONESIA Abraham S Khow*) Faculty of Fisheries and Marine Sciences, Pattimura University, Ambon 97123 Indonesia Received : June, 21, 2006 ; Accepted : December, 12 , 2006 ABSTRACT Monthly shell-length frequency distributions were used to analyse the size and age structure of the limpet population inhabiting the rocky shore of Ohoiwait, Southeast Moluccas. The lengths of the collected specimens ranged from 8.0 to 31.8 mm. The analysis of the successive frequency distributions suggested that the population consisted of 4 to 5 distinct age groups (cohorts) at any given time, and that two new cohorts recruited during the one-year investigation period. An analysis to determine growth pattern using FiSAT software showed that the longevity of C. testudinaria extended up to 2 years. The values of von Bertalanffy growth parameters (L∞, K and t0), estimated from size-frequency distributions, were 33.1 mm, 1.4 yr-1, and 0.09, respectively. The highest growth increments were 25% and 18% of the asymptotic length during the first 3 and 6 months, respectively. The effects of environmental variables on the growth rates showed important seasonal variations, with the highest increment of 2.6 mm/month during dry season. Here, growth parameter of C. testudinaria limpet shows the same value as other tropical limpets and depends on environmental variables. Key Words: Shell-length frequency distributions, Growth determination, Cellana testudinaria. *) Correspondence: Phone +62-81343044295, E-mail: [email protected] INTRODUCTION The tropical limpet C. testudinaria is A burst of theoretical contributions reasonably well known from systematic and regarding estimation of growth parameters geographical distribution aspects (Wilson, from growth data (Lotze, 1998; Khouw, 1993; Attrill et al., 2001), but there are little 2002) has led to the clarification of the published studies regarding its growth or concept of the effects of environmental other aspects of its biology. Many variables on the growth of limpets (William investigations about growth rates of various & Morritt, 1995; Liu & Morton, 1998). Patellacea have been carried out focusing on Iwasaki (1998) examined growth rates of several factors affecting growth, such as some tropical gastropods in an attempt to tidal height (Takada, 1997; Williams et al., determine whether life spans were under 1999), water temperature (William & primary temperature control as suggested by Morritt, 1995; Saad, 1997), seasonal changes and food availability (Brêthes et al., 1994; Ruiz Sebastián et al., 2002). Growth Determination Of Tropical Limpet Cellana testudinaria (Linnaeus, 1758) Living On The Rocky Shore Of Ohoiwait, Southeast Moluccas, Indonesia 89 Journal of Coastal Development ISSN : 1410 - 5217 Volume 10, Number 2, February 2007 : 89 - 103 Accredited : 23a / Dikti/Kep/ 2004 Levins (1968) or whether some other Therefore, this research would present features of the milieu of these animals information on the growth rates of C. determined their longevity. In a review of testudinarai and some factors presumably the physiological variation among intertidal affecting them. Moreover, the results are molluscs, Dunmore & Schiel (2000) compared it with those of similar limpets concluded that on the whole southern from temperate regions. hemispheres, species have shorter life span and attain smaller final size than northern ones. The evidence from the north Atlantic ATERIALS AND ETHODS and Pacific coasts of North America M M indicated that this generalization also holds Study site within species with broad latitudinal distribution (Dunmore & Schiel, 2000). These findings imply that differences of The study was carried out monthly on the intertidal rocky shore of Ohoiwait growth parameters between limpets in 0 0 different regions can be explained either by (latitude 5 45’15” S, longitude 132 57’20” a single primary environmental effect or E), Big Kai Island, Southeast Mollucas, may result from a combination of interaction Indonesia (Fig. 1) from October 2001 to September 2002. The intertidal region between environmental and other factors. 2 C. testudinaria is an excellent investigated is about 0.25 km (1 km long species to study growth, as they are present and 0.25 km wide). Thus, it is small enough in high numbers, range freely on all rocky that atmospheric conditions may be substrata, and the shells of these animals assumed, for most purposes, to be uniform show distinct dimensions, suggesting a over the whole area. The shore consisted of possibility for determining growth. The shingles, pebbles, medium and big boulders notion that environmental stress is generally of about 90% of covering substrate. The an important factor which directly or physical conditions in the tidal zones are indirectly influences the population quite different; the higher shore is wetted dynamics of common intertidal animals almost exclusively by tidal sea level rise, but (Lohse, 1993; Delany et al., 1998; Brey, the lower shore receives considerable wave 2003; Clarke et. al., 2004) has led this study action. to further examine the same hypothesis. Growth Determination Of Tropical Limpet Cellana testudinaria (Linnaeus, 1758) Living On The Rocky Shore Of Ohoiwait, Southeast Moluccas, Indonesia 90 Journal of Coastal Development ISSN : 1410 - 5217 Volume 10, Number 2, February 2007 : 89 - 103 Accredited : 23a / Dikti/Kep/ 2004 N 5°18' ∗ Banda Sea 5°26' 5°34' 5°46' Ohoiwait 5°54' Arafura Sea S 132°34' 132°42' 132°50' 132°58' E Fig 1. Map of study site of Ohoiwait located at the Big Kai Island. Growth measurements mean sizes of cohorts were followed through time. The population of C. testudinaria was sampled periodically and the mean size Analyses of the individuals within distinct age cohorts was calculated from polymodal size- Population structure. The frequency distributions (Tablado et. al., population structure of C. testudinaria was 1994; Turon et al., 1995; Murray, 2002). analysed using the Modal class Progression Age classes were defined through analysis Analysis, MPA (Gayanillo et al., 1996) by of length frequency distributions to the aid of FiSAT software (Sparre & decompose monthly size-frequency into Venema, 1998). This methodology infers their component normal curves (Brêthes et growth from the apparent shift of the modes al., 1994). The estimate of growth used the or means in a time series of length frequency monthly size of frequency data, whereby the samples. It was then applied to the Growth Determination Of Tropical Limpet Cellana testudinaria (Linnaeus, 1758) Living On The Rocky Shore Of Ohoiwait, Southeast Moluccas, Indonesia 91 Journal of Coastal Development ISSN : 1410 - 5217 Volume 10, Number 2, February 2007 : 89 - 103 Accredited : 23a / Dikti/Kep/ 2004 frequency histograms of the limpets’ shell Bartlett’s test (Sokal & Rohlf, 1995) was lengths to divide them into distinctive used to check the assumption of cohorts. homogeneity of the residual variances Growth. The growth of limpets was before using ANCOVA. analysed by using the most widely used being that developed by von Bertalanffy (1938) that has been known as the RESULTS AND DISCUSSION - K (t – to) Bertalanffy equation: Lt = L∞ [1 – e ] where Lt is the length at age t, L∞ is the Population structure asymptotic length (representing the maximum theoretical length of animal), K The size structure of the population the growth coefficient (describing the rate of of C. testudinaria was examined through the growth of the animal to its maximum size), analysis of percentage size frequency and to the theoretical age at length 0 (the distribution (Fig. 2). The overall specimen start of growth of the settled larva); the sizes ranged from 8.0 to 31.8 mm, intercept between the curve and the t axis. representing 6 cohorts. The first cohort Statistical analysis. Seasonal consists of juvenile limpets with an average variation in the growth of cohorts was length of < 10.5 mm, representing 13 % of assumed to be negligible in the present the total population. The second cohort study, because growth rates calculated at encompasses the limpets with lengths of different times could confound an analysis 10.5 – 15.5 mm, accounting for 48 % of the of seasonal variability. As a consequence, I total population. This sub-population proceeded with the comparison of regression generally presents the group of limpets with lines resulting from the relationships the highest growth rates. The remaining between shell length and the number of cohorts consist of limpets with an average months, using an analysis of covariance length of 15.5 – 20.5 mm, 20.5 – 25.5 mm, ANCOVA (Sokal & Rohlf, 1995). This test 25.5 – 30.5 mm, and > 30.5 mm, accounting determines the level of similarity between for 22 %, 9 %, 7 %, and 1 % of the total the samples, and, in case of heterogeneous population, respectively. relationships, obtained the nature of the source of the differences (Baxter, 1983). 20 18 16 14 12 10 8 6 4 PercentageFrequency (%) 2 0 8,5 9,5 10,5 11,5 12,5 13,5 14,5 15,5 16,5 17,5 18,5 19,5 20,5 21,5 22,5 23,5 24,5 25,5 26,5 27,5 28,5 29,5 30,5 31,5 Mean length (mm) Fig 2. Cellana testudinaria. Mean percentage frequency of each size class category. Vertical lines represent standard deviation (SD). Growth Determination Of Tropical Limpet Cellana testudinaria (Linnaeus, 1758) Living On The Rocky Shore Of Ohoiwait, Southeast Moluccas, Indonesia 92 Journal of Coastal Development ISSN : 1410 - 5217 Volume 10, Number 2, February 2007 : 89 - 103 Accredited : 23a / Dikti/Kep/ 2004 Growth 8.5 mm to 31.5 mm and the smallest limpets (8.5 – 10.5 mm) are assumed having All monthly size-frequency histograms settled 2 months before being sampled are polymodal; 4 modes were found in (Fig.