Task 1: Bio-Physical Transport Model

Sub-tasks 1.1 and 1.2: Development and Application of the model

Model development will concentrate on the development of Individual-Based Modules of growth and mortality of larvae and post-larvae for incorporation in a physical transport model. Using observed wind data for individual years and variations in wind patterns, model simulations will be carried out for the drift and survival of eggs, larvae and post-larvae of mackerel allowing for growth and mortality in relation to environmental conditions during their planktonic drift.

• The circulation model (based on the HAMSOM model - HAMburg Shelf Ocean Model) feeds the physical parameters to the Bio-Physical Transport Model.
• The three-dimensional position of each particle is calculated using the current field and the vertical migration routine.
• The growth rate of each particle at each model grid point is determined as a function of temperature, food availability and its size calculated.
• Each particle is transferred to the mortality module where the chances of survival are determined, depending on controlling parameter values and the updated information implemented for the next model iteration.

The principal biological input to the model will be parameterizations of the distributions and abundance of the planktonic and early nektonic stages of mackerel (eggs, larvae and post-larvae) and their growth, mortality and vertical distribution in relation to environmental conditions (principally, temperature and food availability). Data will be obtained from analysis results of the ICES Triennial eggs survey samples and from more detailed sampling on SEAMAR cruises.

Sub-task 2.1: Geographical distribution of eggs, larvae and post-larvae

The model simulations will be initialised with egg distribution data from the ICES Triennial surveys. Larval and post-larval distributions, from Triennial samples and from cruise sampling using a variety of plankton and micro-nekton samplers, will be used for validation of model output and for studies of relationships with environmental conditions.

Sub-task 2.2: Patch structure, behaviour and vertical distribution

The fine-scale distribution and abundance of mackerel larvae and post-larvae will be studied for use in fine tuning the model functions for diffusion and vertical distribution. Primarily, this will include measures of ontogenetic and diel changes in vertical distribution and indices of aggregation. Most of the sampling will be on the research cruises using gear such as Bongo, MIK, RMT Multi-net, LHPR and neuston nets.

Sub-task 2.3: Growth and mortality

For measures of the growth and mortality of larvae and post-larvae in relation to the physical and biological environment from research cruise sampling and from the 1998 triennial egg surveys. The main methods will include regression analysis of length-frequency abundance data and ageing from otoliths of larvae, post-larvae and recruits. Supplementary information will be obtained from various condition analyses (C/N, RNA/DNA and lipids).

Sub-task 2.4: Feeding, food availability and regional productivity

For information on feeding, food availability and production for parameterization of larval growth and mortality in terms of food availability. It will include gut contents analysis, including the incidence of cannibalism, and measurement of ambient food concentration as numerical counts and size-fractionated dry weight and carbon. Chlorophyll a measurements both from cruise observations and satellite-derived data will be used in sub-models for estimates of primary and secondary production (see also Sub-task 4.1).
 

Data from recruit surveys, in combination with VPA based recruit indices, will be used to derive year-by-year estimates of year-class strength for comparison with model simulations of relative survival through to the late post-larval stages. Sampling of the recruits will also provide otoliths for determining growth history as input to the model. Co-operation will be maintained with complementary EU projects on standardising groundfish surveys (SETITS) and on mapping the distribution of recruits of pelagic species, including mackerel, in the southern area of the SEAMAR study (JUVESU).
 

Sub-task 4.1: Satellite imagery

Satellite imagery will provide: (a) large-scale fields of sea-surface temperature (SST) and indices of primary production for validation, initialisation and updating the SEAMAR model and secondary production sub-models; and (b) historical and near-real time monitoring of mesoscale structures to plan and guide fine resolution cruise patch studies. Data sources will include Advanced Very High Resolution Radiometer (AVHRR) for sea-surface temperature and Coastal Zone Color Scanner (CZCS), Ocean Colour and Temperature Sensor (OCTS), Sea-viewing Wide Field-of-view Sensor (SeaWIFS) and MODIS for phytoplankton pigment concentration, and primary production estimates.

Sub-task 4.2: Ship-based measurements (hydrography)

Standard ship-based hydrographic observations will be made for the detection of mesoscale features and to characterise the local physical environment in relation to concurrent biological sampling. Sampling methods will include CTD casts with added sensors e.g. for chlorophyll a fluorescence, oxygen concentration, light and nutrients, OPC sampling, UNDULATOR tows fitted with sensors for temperature, conductivity and chlorophyll a and ADCP systems for model parameter values and comparison with the output from the circulation model.
 

Data management uses an ORACLE database for the collation of all SEAMAR plankton and environmental data and includes a dynamic hypertext link to the satellite imagery.