Growth estimations of the Argentinean wedge clam Donax hanleyanus: A comparison between length-frequency distribution and size-increment analysis

Growth rates of the Argentinean wedge clam Donax hanleyanus were estimated comparing two different methods in the intertidal of the exposed sandy beach Mar de las Pampas: (i) results of a relatively shortly (49 days) tagging-recapture experiment using the in situ fluorescent marking (IFM) method and subsequent size-increment analyses were compared with results from (ii) length-frequency distributions (LFD) analysis originating from a time consuming 25 month quantitative sampling. Residuals, derived from IFM method and LFD analysis, were of similar magnitude and distribution, indicating that both methods are equally appropriate to estimate growth of D. hanleyanus. Comparing overall growth performance indices (OGPs) of several Donax species from different climate areas it resulted that growth of temperate bivalves can be estimated well by carrying out a relatively short-time tagging-recapture experiment using IFM but it is recommended to use both, the IFM as well as the LFD method to determine growth of tropical bivalves. Furthermore, an in vitro suitability test of the three stains strontium chloride hexahydrate, alizarin red and calcein resulted that the latter is useful as non-lethal growth marker for D. hanleyanus, emitting a bright green fluorescence band under blue light.