Ben Thornes

Modelling larvae of the invasive Manila Clam

Tuesday 15th July 2014

Invasion in tidal zones on complex coastlines: modelling larvae of the non-native Manila clam, Ruditapes philippinarum, in the UK.

The aim of this research was to evaluate whether natural larval transport and behaviour alone can explain the pattern of invasion and establishment of the non-indigenous Manila clam, Ruditapes philippinarum, and its spread beyond the point of introduction in Poole Harbour.

Data was gathered using fine-resolution hydrodynamic models coupled with a water salinity model and an individual behaviour model of Manila clam larvae. The model was informed by experimental studies on the vertical response of larvae to salinity and field studies of the species in its natural and new environments.

The results showed that variations in the behavioural response of larvae to salinity in the model considerably affected the retention of clam larvae within the harbour. High levels of predicted larval retention occurred in two of five zones in the harbour when the salinity target was set at 17 practical salinity units. Persistently high densities of adult clams and recruits are accurately predicted in these regions.

The article concludes that even within a relatively small region such as Poole Harbour, there is both localised retention of larvae or ‘closed’ areas and areas that are considerably more ‘open’ and potentially connected. The behavioural response of larvae to salinity significantly affected the degree of retention and ‘openness’ of the harbour to this species. Although, through natural transport, larvae could theoretically reach the next available habitat within the duration of the pelagic stage, the study indicates that areas of sufficiently reduced salinity may be necessary for sufficient retention, recruitment and establishment of new adult populations in estuaries. High resolution hydrodynamic models, coupled with larval behaviour, can accurately simulate and predict biological invasion along complex coastlines and contribute to risk assessment of the introduction of non-indigenous species for aquaculture and spatial management of marine protection.

View the results in a video format on YouTube.

Read the full article here.

Find out more about Dr Roger Herbert here.

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