Mussel spat abundance in Scottish waters: is it changing? Keith Davidson. Scottish Association for Marine Science

Transcription

1 Mussel spat abundance in Scottish waters: is it changing? Keith Davidson Scottish Association for Marine Science

2 Scoping workshop towards a better understanding of the factors influencing mussel spat settlement in Scottish waters

3 Attendees Mike Cowling - Crown Estate Alex Adrian - Crown Estate Walter Speirs - ASSG David Fell - ASSG Janet Brown - Editor, The Grower Alan Byrne - Fassfern Mussels Iain MacKay - Loch Fyne Oysters Ltd Gitte Salvarli - Glencoe Shellfish Douglas Wilson - Inverlussa Shellfish David Attwood - Loch Fyne Ian MacKinnon - Arisaig Mussels Lindsay Angus - Seafood Shetland Sandy Cross - Seafood Shetland Ruth Henderson - Seafood Shetland Michael Laurenson - Seafood Shetland Kenny Pottinger - Seafood Shetland Michael Tait- Seafood Shetland Liz Cook - SAMS Eleanor Martin - SAMS Adam Hughes - SAMS Clive Fox - SAMS Christine Beveridge SAMS Keith Davidson SAMS John Craft - Glasgow Caledonian University Halldor Olafsson - Biopol Iceland Andrew Mayes - Marine Scotland Iveta Matejusova - Marine Scotland Scott Campbell - Biosciences KTN

4 Scoping workshop towards a better understanding of the factors influencing mussel spat settlement in Scottish waters Why are we here? Perceived decrease in mussel spat settlement/development in Scottish waters This has led to industry concern This workshop is intended to bring together stakeholders from industry and science to discuss the problem and potential subsequent action

5 Hoped for outcomes from today Information sharing and gathering Common understanding of a need (or not) for further work on the issue Some specific ideas of the direction this work should take (monitoring/study of specific topics etc ) Discussion of how best to facilitate this work

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7 Written report available me at

8 Conclusions from the workshop There was general agreement that a research programme investigating issues surrounding mussel spat settlement and development would be beneficial to the industry in Scotland. The Crown Estate indicated that, should a suitable proposal be prepared, it would be considered for funding. It was suggested that this research programme be a pilot project be conducted at contrasting sites (of high and low spat recruitment to be guided by industry).

9 So where are we now? Close to submitting a proposal Content has been developed in conjunction with industry In particular Ruth Henderson & Michael Tait Also, Douglas Wilson, Cree McKenzie, Walter Speirs

10 Proposal has three components: Work package 1: Literature survey/ shellfish farm survey Work package 2: Field monitoring and statistical interpretation of spat settlement and environmental factors that may influence this and subsequent spat development Work package 3: Modelling and ground truthing of mussel spat transport/dispersal.

11 Work package 1 Part 1: Literature review. To our knowledge there has been no systematic review of the scientific evidence related to mussel spat abundance, settlement and development either within or outside of Scotland We shall address this.

12 Work package 2 Field monitoring and statistical interpretation of spat settlement and environmental factors that may influence this and subsequent spat development 3 years field work, with frequent sampling 4 proposed sites Loch Spelve (Argyll) Loch Roag (W. Isles) Bixter (Shetland) Clift Sound (Shetland)

13 Biological quantities Spat abundance Spat settlement influence of substrate influence of depth Spat quality

14 Spat abundance

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18 Meat yield Slide from Newfound Aquaculture Industry Association Handbook of Mussel Farm Site Monitoring (2000)

19 Substrate

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21 SPAT quality: glycogen Gylcogen is a polysaccharide that serves as a form of energy storage

22 Temperature Temperature LY Depth (M) Mar-09 Apr-09 May-09 Jun-09 Jul-09 Aug-09 Sep-09 Oct-09

23 Salinity Salinity C Depth M Mar-10 Apr-10 May-10 Jun-10 Jul-10 Aug-10 Sep-10 Oct-10

24 Chlorophyll Fluorescence LY1 5 Depth (M) Mar-09 Apr-09 May-09 Jun-09 Jul-09 Aug-09 Sep-09 Oct-09

25 Phytoplankton community composition

26 Weather

27 Caprelid grazers Reduced spat settlement has been linked with the presence of the invasive non-native caprellid amphipod, Caprella mutica (Boos et al. 2011). Photo: E. Cook (SAMS) Photo: F. Kerckhof

28 A Giant Caprellid in Scotland what do we know so far? Origin: North-west Pacific Introduced via ballast water, hull fouling or aquaculture (Oyster spat?) Adult length; 25 to 40 mm (males); 10 to 15 mm (females) Reproduce from July to November each year (peak in September); high reproductive output per female Extremely abundant at fish and shellfish sites throughout west coast of Scotland; >300,000 ind.m -2 recorded in summer months Distribution of C. mutica on the west coast of Scotland (Ashton et al. (2007) Hydrobiologia 590: ), plus additional sightings 56

29 crabproject.com apps.acesag.auburn.edu Dietary Preferences Highly opportunistic Stomach content analysis has shown predominantly detritivore (Guerra-Garcia 2009) BUT will feed on suspended particles using setae on antennae and has been observed in lab trials consuming average 15 Artemia nauplii hr -1 (K. Boos, pers. comm.) Artemia nauplii, <0.4 mm when first hatch Able to consume variety of diet types of similar size to Mytilus D larvae Mytilus edulis D larvae, typically <0.35 mm in plankton

30 Results from this preliminary trials suggest that C. mutica (<16.5mm) do not predate on or affect the settlement success of M. edulis in the later stages of its larval phase (i.e. > 250 µm) BUT Adult male C. mutica can reach a maximum body length of 40 mm. Therefore, size specific feeding behaviour must be taken into consideration for the various life stages of C. mutica Mytilus D larvae may be preyed on by larger C. mutica, but this needs further investigation Caprella mutica at Dunstaffnage Fish Farm E. Cook, SAMS

31 Work Package 3 Modelling of mussel spat transport/dispersal important to determine if the bulk of spat is generated within or outside the localised water body and if factors such as the state of the tide influence either transport into or retention within the loch.

32 Asimuth model: Unstructured grid model

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34 Physical simulations T S

35 FVCOM Cell Tracking

36 Work Package 1 Part 2: Shellfish farm survey On receipt of reports of poor mussel settlement and mortality in 2010, Marine Scotland Science issued a questionnaire to Scottish mussel farmers. This sought to: Gauge the significance of the reports Consider possible action to minimise their impact Advise on the need for research and development Many businesses reporting poor or absent spat fall in recent years, local changes in the timing of spat settlement and with individual site mortality events also being evident. Survey indicated that spat fall monitoring is not undertaken routinely on farm sites Spatial and temporal variation in spat settlement is not known in Scotland!

37 This project offers the opportunity to conduct a spat survey If it is to be worthwhile we need the wider industry to buy in to the project and contribute to the farm survey component of work package 1

38 With Thanks to Michael Tait (North Atlantic Shellfish) for the initial suggestions. For each site suggested parameters to record are: Spat abundance? But also: Length headline? No. of droppers depth? Spat year class? Month collected? Type of ropes used? Location of spat collected? Method of collection? Collection depth? Spat quality? Reseeded in? Shrimps present? Starfish present? Ducks present? Results will be annonomised and returned to participants

39 Line number Length Headline no of droppers/m dropper depth Spat year class Month collected Type ropes used spat Location of collection spat collection Method collection depth Spat quality Reseeded in Shrimps observed star fish present ducks present month of treatment m June Power loop Bixter site Itstakorda 3 core 0-6m excellent from spat site - Bixter no no yes m June Power loop Bixter site Itstakorda 3 core 0-6m excellent from spat site - Bixter no no yes m June Power loop Bixter site Itstakorda 3 core 0-6m excellent from spat site - Bixter no no yes m n/a Power loop Harvest stock ex harvest resock no no yes drops July pegged ropes in situ natural 0-10m good n/a no no yes drops July pegged ropes in situ natural 0-10m good n/a no no yes drops July pegged ropes in situ natural 0-10m good n/a no no yes

40 Now is your chance to influence the design of this survey (or indeed whether it is conducted at all). I ve left copies of the current suggested survey design on the tables. Along with a sheet for adding comments. Please complete these today and return to the box I ve left at the registration desk or contact me by keith.davidson@sams.ac.uk

41 Thanks to.. Workshop participants The Crown Estate Ruth Henderson, Michael Tait Walter Speirs, Douglas Wilson, Cree McKenzie Elizabeth Cook, Clive Fox, Adam Hughes, Dima Aleynik, Tom Adams