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Population and ecophysiological modelling of the cultured mussel Perna perna : towards the development of a carrying capacity model

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Suplicy, FM (2004) Population and ecophysiological modelling of the cultured mussel Perna perna : towards the development of a carrying capacity model. PhD thesis, University of Tasmania.

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Abstract

The overall aim of this thesis was to integrate the ecophysiology and population
dynamics of the mussel Perna perna in Southern Brazil into a model that can ultimately be
used for carrying capacity analysis in a tropical environment. The first chapter quantified
and modelled the filter-feeding behavior of mussels feeding on natural seston. Models
were generated that described each step of the feeding process and produced a predictive
model of rates of food uptake. Feeding experiments using the biodeposition approach were
conducted with mussels ranging in shell height from 3.94 to 9.22 cm of three sites,
including turbid and clear water environments. Among the feeding steps characterized and
modelled were filtration rate, rejection rate, organic selection efficiency, the organic
content of ingested matter, absorption efficiency, and absorption rate. The coupling of the
equations that described filter-feeding processes produced a robust model with relatively
low complexity and specificity. The model can predict the P. perna feeding behavior in
turbid or clear water and can be used with different species if the correct coefficients are
used.
In the second chapter, growth and mortality rates using size frequency
distributions of P. perna in suspended culture in two locations were studied. Growth
rates were used as forcing functions in a model to predict size class distributions on one
meter mussel ropes. Settlement of new individuals was included in the model using the
unique settlement rate observed in each location. Mortality rates were estimated at 0.06
year-1 in the populations at both locations. The integration of growth and mortality data in a predictive model resulted in good predictions of size frequency distributions at two
locations in Brazil.
The third chapter coupled the feeding model developed earlier with a model of
energy balance and scope for growth. This model was divided in four sectors to facilitate
description and explanation of the functions controlling feeding and metabolic responses
to varying food availability and seawater temperature. The seston sector included
characteristics of seston likely to influence food and energy acquisition in mussels. It
also included relationships that estimated the energy content of phytoplankton and
detritus, the main components of mussel diet. The feeding sector described suspensionfeeding
behavior using natural seston as described in the first chapter. In the energy
allocation sector, absorbed matter was transformed to absorbed energy using estimates of
energy content of food provided in the seston sector. After accounting for the
maintenance requirements of the mussels (heat loss, excretion, and mucus production),
the scope for growth was directed to the growth sector. The growth sector included
byssus, organic shell, and soft tissue production based on energy pa,rtitioning estimated
from monthly measurements of tissue (somatic and reproductive) and shell growth. The
model successfully predicted mussel shell length and dry tissue weight during the
simulation period and estimated the response of mussels to food acquisition, energy
expenditure, and allocation to growth.
In the fourth and last chapter, mussel population dynamics and ecophysiology
were coupled to model feedbacks from the bivalve population to the environment. These feedbacks included population level estimates of the rates of filtration, excretion, and
biodeposition. Seston (TPM, POM and CHL a) dynamics were investigated in three
temporal scales: biweekly for four years, weekly for eight months, and tidally (neap and
spring tides). Characterization of the study area enabled an estimation of bivalve
standing sock, total surface area, and volume of the area. Measurements of water level
across tides allowed estimates of tidal water renewal inside the area. Some aspects of
interest for carrying capacity analysis presented in the last chapter were the water mass
residence time for the area, bivalve clearance time (the time needed for the total bivalve
biomass to filter a volume of water equivalent to the system volume), and phytoplankton
production time (the time it takes for the primary production within the system to replace
the phytoplankton biomass within the system).
Among the important aspects for carrying capacity studies not included in this
model are the spatial resolution of hydrodynamics_ processes and physical/biological
processes related to seston dynamics like sedimentation, resuspension, and mineralization
of organic compounds, interacting together with the population ecophysiology to predict
the exploitation carrying capacity for this system. Although there was good agreement of
the model prediction with the observed mussel growth data, the model needs to be tested
with an independent set of data before it is can be used as a management tool. Therefore,
it appears that the integration of whole animal models with population models can be
used in carrying capacity analysis for shellfish culture areas in Brazil.

Item Type: Thesis (PhD)
Keywords: Mussel culture, Perna
Copyright Holders: The Author
Copyright Information:

Copyright 2004 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2004. Includes bibliographical references

Date Deposited: 04 Feb 2015 23:30
Last Modified: 11 Mar 2016 05:54
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