Match/mismatch between biological and management units

Two types of spatial units

BIOLOGY MANAGEMENT Populations Stocks

The historical demarcation of the ICES distribution areas is a measure of convenience. It implies gross simplifications and assumptions on the biology of the fish. The spatial organisation of the true population structure, connectivity and life-history traits are not taken into account in the ICES areas. In addition, the associated overexploitation leads to loss of genetic diversity and potential to adapt. Key Questions: 1. What levels of genetic differentiation between populations justify

treatment as stocks that are managed separately? 2. How are these populations interrelated?

Genetics to unravel population processes

Connectivity of turbot and brill populations in European waters as a basis

for sustainable management

Sara Vandamme1,2, Kelle Moreau1, Gregory Maes2, Daan Delbare1, Stefan Hoffman1 and Filip Volckaert²

1Institute for Agricultural and Fisheries Research, Animal Sciences – Fisheries, Ankerstraat 1, 8400 Oostende, Belgium

² Katholieke Universiteit Leuven, Laboratory of Animal Diversity and Systematics, Ch. Deberiotstraat 32, 3000 Leuven, Belgium

Similarities in biology, fishery and current management

Habitat: sandy and stony bottoms down to 70 m, both salt and brackish waters Juvenile diet: benthivorous; adult diet: mainly piscivorous Spawning: April - August, pelagic eggs

By-catch species in fisheries targeting demersal fish (sole, plaice, dab, cod, …) Fishing methods: bottom trawls (beam and otter), gillnets, trammel nets, long lines High commercial value

No analytical assessment, only advice in Baltic based on historical trends EC requests analytical advice for all areas

Measure Biological info Application

Genetic Variation - Allelic diversity, A - Genetic consequences of demographic - Biodiversity conservation

- Heterozygosity, H processes: population fluctuations, - Genetic effect of MPAs

- Inbreeding, FIS reductions & bottlenecks - Genetic imprinting of fishing

Abundance - Effective population size, Ne - Population dynamics - Stock assessment & management

- Reproductive succes - Recruitement prediction

Structure and - Spatial genetic differentiation - Population structure - Management units definition

connectivity FST, RST, GST, D - Gene and migration flow - Delineation of MPAs

- Temporal genetic divergence - Mixed fisheries assessment

FST-Temporal

ABOVE Distribution and density of turbot in Europe

(fishbase.org). Brill has a similar distribution with much

lower densities in the Baltic and Black Seas.

Turbot Psetta maxima (© Luc Viatour)

Institute for Agricultural and Fisheries Research, Animal Sciences – Fisheries

Corresponding author: Sara.Vandamme@ilvo.vlaanderen.be, +32(0)59/569896

other

COD

PLE

SOL SRX

INV TUR BLL

Landing-shares Belgian vessels 2000-2008 (tons)

Value-percentages Belgian landings 2000-2008

OTX

COD

PLE

SOL SRX

INV TUR

BLL

COD

PLE

SOL SRX

INV

BLL

TUR

RIGHT Relative importance of turbot and brill in A) Belgian

landings (all harbours) and B) Total Value of these

landings, summed over the period 2000-2008. Note that

both species show a significantly larger share in the value,

illustrating their high commercial values.

OTX

Landings

Value

COD = Cod Gadus morhua PLE = Plaice Pleuronectes platessa

SOL = Sole Solea solea SRX = Skates and Rays (Rajidae)

TUR = Turbot Psetta maxima BLL = Brill Scophthalmus rhombus

INV = invertebrates (crustaceans, shellfish and squid)

OTX = all other fish

Areas for stock

assessments defined by the

International Council for the

Exploration of the Sea

(ICES; www.ices.dk)

Belgian Beam trawler (© Kelle Moreau)

Future work: Delineation of biological populations based on genetics Characterisation and quantification of connectivity between populations Development of an appropriate assessment method taking these results into account