About the TABACOD project

Background

The biological advice for cod management in the eastern Baltic Sea is currently hampered by lack of proper assessment of the status of the stock.

Deteriorated quality of some basic input data for stock assessment in combination with changes in environmental and ecological conditions has prevented an analytical assessment of the stock. Since 2014 it has not been possible to quantify the present stock status with the information available.

One of the key issues that prevent understanding the present status of cod and providing adequate management advice is lack of information on true age of cod. Inconsistencies in age interpretation have become increasingly problematic and prevent the estimation of fish growth. This has consequences both for stock assessment and fisheries management. 

TABACOD objectives

The objectives of the TABACOD project are to provide information on growth and mortality of the Eastern Baltic cod to aid in solving the issues with stock assessment and establish a solid scientific basis for cod management in the Baltic Sea.

This requires two interlinked tasks: 

  1. establishment of a spatially comprehensive sample of cod with “known growth” over a known time period to understand the present status of the stock
  2. the development of an objective method that continuously allows deriving growth information in the future.

Two methods that will yield the necessary information are i) tagging of individual fish and ii) analysis of the chemical composition of their otoliths.

The aims of a tagging program are thus to provide information about size-specific growth of Baltic cod for stock assessment and current fisheries management purposes, but also to serve as validation for otolith chemistry-derived growth estimates. The chemical analysis of otoliths on the other hand will provide a cost-efficient tool for estimating growth in historic and future samples after the termination of the tagging program. 

Work packages


Work package 1: Historic tagging data

Objectives: Compile data from historic tagging experiments

Data from historic tagging experiments will be collated to provide the empirical information for the development of statistical growth models for stock assessment purposes. A substantial body of data will be made available to this project, the majority thereof from several large-scale tagging projects.

Work package 2: Tagging program

Objectives: To design and carry out an international tagging program

In this work package an international tagging program involving all countries with a major fishery in the Baltic Sea will be designed and carried out. It will involve the identification of the best practice for tagging, raising public awareness of the project, handling of a reward system for delivery of recaptured fish, handling the data emerging from the recaptured fish and maintenance of a common database. For successful reporting of recaptures it is essential that all actions are coordinated internationally.

A total of 20’000 cod will be tagged with T-bar tags over the years 2016-2019, with an additional 2’000 cod tagged with electronic Data Storage Tags recording temperature and depth.

Work package 3: Data analysis for stock assessment

Objectives: Development of statistical growth models, independent estimates of mortality and implementation of tagging/growth data in stock assessment models

In this work the results obtained from work package 1 and  work package 2 will be synthesized. The aim is to use these data to develop validated growth models and implement the use of tagging/growth data in stock assessment models.

Within this work package we will also develop a manual for how to implement the best-practice routines for obtaining growth information in the future.

Work package 4: Method for future growth estimation 

Objectives: To develop and implement a method for estimating fish growth based on otolith chemistry

In this work package we will develop a method for estimating a cod’s growth based on the chemical profiles of all relevant elements from hatch to capture. The method development will be based on already existing otoliths of known age and/or growth but from a restricted size range described in work package 1. This otolith chemistry-based method will subsequently be validated with analysis of otoliths from cod tagged during this project (work package 2).

 

http://www.tabacod.dtu.dk/dansk/about
6 DECEMBER 2019