Didemnum. The first 5 years at Edmonds, WA. Tunicate Control Efforts by Volunteer Recreational Divers focused on Didemnum cf lahillei

Transcription

1 Didemnum The first 5 years at Edmonds, WA Tunicate Control Efforts by Volunteer Recreational Divers focused on Didemnum cf lahillei Bruce Higgins Volunteer Coordinator Edmonds Underwater Park, Edmonds

2 The Underwater Park A City of Edmonds Park having no-harvest protection with diver focused features of 27 acres north of Edmonds Ferry Terminal The site hosts about 25,000 divers annually Volunteer diver stewardship effort started in 1977 works to keep the Park a haven for life and recreation

3 The Park s Southern half - just north of the Ferry Terminal >> The site of the first colony The bottom is mostly sand * ( * Site of Triumph)

4 The Park s Northern half features are all offshore of the eel grass Near shore there is a gravel and cobble area that host a kelp bed Initially (2004) there were no colonies in this area

5 Volunteer Effort Background The Tiered Action Plan is: Safety Security Maintenance Enhancement Coping with the Tunicate is under security of the Park Resources as we try to deal with all invasive species as well as poaching As a self funded effort we try to be decisive, efficient, and effective in our actions We are diving every weekend so there is constant attention to the Park s needs with about 1,700 volunteer hours per year

6 Methods Control Measures We realized in 2004 that this would now have to be part of our routine activities as the invasive species don t quit they have seasons just like all the other life in the Park. We realized that we had to be adaptable as the effort in 2004 was just too much time to invest routinely so we had to be more effort as we better understood how Didemnum behaved The goal was to keep spread out of the Park as long as possible and minimize its impact

7 Typical Tunicate: Didemnum grows as colony of individuals the size of ½ grains of rice in a mesh that looks a lot like a 5mm layer Its give away is it covers pioneers like muscles, barnacle, like a carpet

8 Tunicate Specific Control Existing extent of Didemnum cf lahillei - Flags for marking the existing extent (Tyvek nailed to hull) Tags as needed so sites can be revisited - Drawings / sketches as to location(s) - Full park survey for patches of scale done in waves due to scale of Park. - Candidate sites recorded, labeled - Null observations recorded as well so sites not needlessly revisited

9 Control - 2 2) Enclosure => Isolation Containment reproduction / growth hindered Starvation / Suffocation / Goal is death with minimum impact ( x 3 area of wooden hull covered) Wrapping with clear food wrap worked well on smaller areas (Wrapping with craft paper or wax paper did not work) An enclosures worked on the steel rudder in 2005 but needs to be suitable scale

10 Prior to Enclosure Triumph 02 Oct cm marks on rod (Jim Middleton, Photo by Kirby Johnson)

11 Enclosure on Triumph 02 Oct 2004 (10 x3 ) (Bruce Higgins, Photo by Kirby Johnson)

12 Control - 3 3) Treatments only in 2004, 2005, and 2006 After consultation with DWFW applied Sodium Hypochlorite Tablets (crushed) 2 treatments (9 th and 16 th Oct 2004 Water samples for Dept of Ag on treatment level in 2004 Treatments in 2005 and 2006 have been table salt so far used about 15 tablespoons a year seems adequate Inside the snug enclosures seems toxic enough Since treatments are problematic other methods were applied (treatments could return if considered of value)

13 Treatment Photos -JD Rowe After 17 days Sodium Hypochlorite treatment (these photos were taken on 25 th Oct 2004) Top suffering Middle dead Bottom decaying

14 Control - 4 Direct removal where practical The buoy lines in the Park seem an obvious item that can be traded out for new lines. Death by drying out and freshwater on the beach (well away from High Tide line) This proved very labor intensive was used in 2004,5, & 6 Burial Covering the colony with sand has become the method of choice. Always available can be done on the spot and seems very effective less than a week and we can t find viable colonies. Requires no tools except your hands to scoop sand from the bottom to cover the tunicate colony.

15 Control - 5 4) Routine monitoring Inspection Video and Photo documentation of early efforts but this became too much work. Direct observation as part of a routine part of dives to look and act Continued inspections as part of annual ling cod nesting surveys Dec to April include observations for Didemnum Continued inspections as part of buoy maintenance and other Park projects Notations made as to locations and time of treatment so follow-ups can occur as resources permit

16 Results 1) Treatment in 2004 appears a success after 50 days 2) Identification was initially difficult Provided divers with magnifying glass (for U/W use) helped A training class was great assistance due to color variations Used invasive behavior over specific biological characteristic, like covering sea weeds with layers 3) Seasonal attention is what is needed as peak growth appears to be late July into September. It appears to us to wait for the second plankton bloom to do it growing. 4)Color varies in the Park and is not an good indicator. Behavior is the most revealing as it can cover various red kelps in just weeks.

17 5) Documented and labeled candidate sites for follow-up investigation is lots of work it seems best to deal with colonies as they are spotted. 6) Careful removal by recreational divers is not a viable option (at least at Edmonds) do to pace of diver s progress and concern about spreading, other techniques like burial if possible is the method of choice. Re-growth has occurred so continued inspections are required. 7) Sadly we have observed colonies at the Port of Edmonds, at the Edmonds Ferry Terminal, and prior to removal at the Marina Beach Pier. Also sadly no efforts of monitoring or control seem to exist at these sites.

18 Sites observed: (not including buoy lines or trail) * * * *

19 Cathedrals Site 5 09 Nov 2004 JD Rowe 9 days later / Saran + Salt

20 Cathedrals Site 4 31 Oct 2004 JD Rowe Saran Enclosed + Salted

21 Cathedrals Site 4 09 Nov 2004 JD Rowe 9 days later Saran Enclosed + Salt

22 Conclusions We will be applying our limited resources to eradication and control in a consistent effort. Our main resources are time / energy / talent Our goal remains a quality recreation experience in a diverse environment, with no invasive species. A nursery of native critters not invasive ones. Invasive species are in a resident condition in Puget Sound so the efforts have to continue constantly to keep them out of areas like Edmonds. Since the level of observations for invasive species is so limited the actual extent of issue is very underestimated.