Cephalopod recruitment from English Channel Spawning Habitats INTERREG IVA project CRESH Habitat preferences in spawning and juvenile cuttlefish Emma Jackson 1, & Isobel Bloor 1,2, 1 Marine Biological Association of the UK. 2 Marine Institute, University of Plymouth, UK Email: emma.jackson@mba.ac.uk Meeting of the CHANNEL PROGRAM March 30-31 st, Rouen
CRESH Objectives 1) Improve knowledge of habitats most suitable for reproduction on both sides of the Channel 2) Estimate the contribution of different spawning and nursery areas to the recruitment to the stock 3) Assess the factors responsible for successful recruitment (e.g. spawning nursery habitat provision of food and refuge) 4) Propose recommendations for sustainable fishing. 5) Update recruitment estimates and stock assessments Photo: Paul Naylor Photo: Steve Trewhella Photo: Steve Trewhella
Spawning locations How soon after mating do they spawn? How far do they travel? Do they choose a structure? Spring Migration Inshore To specific Locations? EGGS What factors influence Hatching? ADULTS HATCHLINGS What factors influence Maturation? What factors influence Survival? Autumn Migration Offshore Pre-recruitment period Recruitment period Photos: Eggs and background Paul Naylor; Hatchling Steve Trewhella; Mating pair: Paul Parsons
Identifying important mating/spawning grounds Temperature Light period Wave exposure Depth Salinity Current regime Natal homing? Spatial analysis of distribution records Predictive modelling Genetics Tagging Common cuttlefish, courting pair RJ2 (Paul Naylor 07041 351307).jpg Photo: Paul Naylor Photo: Steve Trewhella Photo: Steve Trewhella
Seasonal migrations of cuttlefish in the Channel and Bay of Biscay (Veronique Losada et al, 2007 Legrand unpublished data, presented in Pawson, 1993) Channel population genetically and biologically different to other populations At other locations evidence of isolated subpopulations and important spawning locations, not yet examined for Channel
CHARM II ATLAS MODEL JULY OCTOBER
Collate data on Cephalopod egg locations,environmental variables and habitat structure Distributional data for eggs, juveniles and adults: CRESH experimental surveys (UK surveys to commence in 2010). Collation of existing records Literature review Questionnaires to cuttlefishermen Environmental data: important parameters identified from the literature review. Sea surface temperature (SST), Suspended particulate matter (SPM), depth, substrate, salinity, exposure and currents (many currently being collated alongside MPA datalayers project). Whilst the location of data sources is already known for the English coasts need similar data from France. Benthic habitat data Survey and biotope maps
Study sites: Lyme Bay (Torbay) Bognor Regis Bay of Seine West Cotentin
Spawning substrate b... Photo: Steve Trewhella
Pilot study by University of Caen 2008-2009 : Assess the feasibility of the method (Essais méthodologiques et faisabilité) Combined 2 complimentary methods (Combinaison de 2 types d'observations complémentaires): Parcours à pieds (BMVE) Plongées (PMME) Tube de Sabella pavonina Furcellaria lumbricalis parcours à pied Furcellaria lumbricalis Plongées Zostera noltii Chondrus crispus Soleria chordalis Fucus serratus Soleria chordalis Sargassum muticum Chondrus crispus Sargassum muticum 0 10 20 30 40 50 60 70 80 fréquence des supports utilisés (%) 0 10 20 30 40 50 60 70 80 Fréquence des supports utilisés (%) 10
Photos by University of Caen
Photo: University of Caen The invasive seaweed Sargassum
Photo: Paul Naylor Seagrass Zostera marina
Photo: University of Caen Sabella pavonia tube
Photo: Paul Naylor Film by Manuel Enrique Garcia Blanco, an underwater cameraman and photographer, who works with Ms Fiona Read, a PhD student at the Marine Research Institute in Vigo, Galicia, Spain. http://news.bbc.co.uk/earth/hi/earth_news/newsid_8587000/8587087.stm
Photo: SSFDC
Photo Dominic Flint
2010 egg survey 4 locations on Channel coast: Torbay, Selsey, Langrune-sur-mer, Agon-Coutainville Intertidal survey on foot and two depths diver survey Stratified random sampling within different habitats. Measure number of clutches, estimate number eggs (plus samples counted), staging of development. Also trial of artificial structures (open pots, rope, netting and ASUs)
Tagging Option 1: Tracking large scale movement of individuals from Offshore to inshore Option 2: Tracking fine scale movements of spawners within the inshore habitats From www.vemco.com
Assessing the nursery role Egg/Juvenile densities Juvenile survival Growth Numbers of studies that have assessed Migration to adult habitats
Recruitment sources or sinks Source Higher relative density of juveniles Higher growth rates Higher survival rates Ontogenetic migration to adult habitat Sink Equal or lower density of juveniles Equal or lower growth rates Equal or lower survival No ontogenetic migration to adult habitat Nagelkerken et al., 2001. Estuar. Coast. Shelf Sci., Vol. 51, no. 1, pp. 31-44.
Lay and stay Hypothesis Spawning cephalopods are distributed patchily, spawn indiscriminately on the first structural habitat encountered, hatchlings redistribute to suitable micro-habitats within that habitat or move to others once hatched Evidence from studies in Jersey: seagrass beds supported greater numbers of juvenile cuttlefish than adjacent sand (Jackson, 2003) Can settlement patterns be maintained? Depends on habitat suitability and survival Revolves around two nursery functions: refuge from predators increased foraging efficiency
Assessing the nursery role Juvenile density Food availability, insitu Food accessibility, laboratory Refuge provision, laboratory Genetics? Trace elements?
Summary of main tasks currently being undertaken 1) Obervations and research into cuttlefish records. 2) Examination of habitat preferences and predictions of potential spawning sites. Do cuttlefish just spawn on the nearest available structure? 3) Examination differences in juvenile survival potential from different areas. E.g. Egg exposure to food and air. 4) Identify the recruitment origin of the offshore stock (trace elements and genetics).
Merci pour votre attention Email: CRESH@mba.ac.uk Hotline: 01752 255026 Text: 07806 938789 www.marlin.ac.uk www.unicaen.fr/cresh