Research Reports of the Maria Mitchell Association

Natural Science Research Projects
Dr. Robert Kennedy, Director

1. The Bay Scallop Stranding Survivorship Study

On 13-15 November, 2003, a major storm washed a thousand or more bushels of Bay Scallops (Argopecten irradians irradians) ashore in Nantucket Harbor. Local volunteers returned 500-700 bushels of seed (1 year old) scallops to the harbor. The MMA/ NHS/NSA investigators placed 351 of the rescued scallops in cages in order to measure the effects upon the scallops of the trauma of being stranded on the beach. Seed scallops already in cages (as part of another MMA study) serve as a control population of scallops which had not been washed ashore.

A Maria Mitchell Association Research Project in collaboration with Nantucket High School and the Nantucket Shellfish Association

 

Nantucket High School senior Andrew McCandless presented the Interim Results at the
24th Milford Aquaculture Seminar
New Haven, CT, February 25, 2004

(Use your back button to return to this page from the presentation)

Latest Results 17 November, 2004 - Survivability differences are apparent for those scallops out of the water for more than a few hours. However, all the beached scallops and the control group have spawned.

This an ongoing study.
Latest results and some commentary will be posted as we get them.

 

Control Group: Summer spawned scallops (n=560) put in cages 17 September, 2003.
Wauwinet: Seed: Scallops collected 16 November, 2003 at Wauwinet. Out of water >1 day.
Wauwinet Nub: Fall 2002 spawn scallops, Wauwinet (n=140). Collected 15 November, 2003. Out of water <12 hours.
Pocomo Seed: Collected at Pocomo at waterline (n=80). Collected 15 November, 2003. Out of water ~3 hours.

In all respects the surviving scallops are looking very similar to the control group. The growth rates of all the caged scallops are very similar. The period of no growth from November through early May is the normal period of winter dormancy.

The group of "nub" scallops collected at Wauwinet probably represent a population of scallops spawned in the fall of 2002. They are consequently larger that the rest of the scallops which were almost certainly spawned in the early summer of 2003. We know that the control group was spawned in the early summer of 2003. The sizes of each group were determined by measuring a sample (n=20 for each of the rescued groups and n=80 for the control group) of the scallops.

Comments
Comments by Peter B. Boyce

15 September, 2004  

1. Survivability differences are emerging among the four groups of scallops.

Frank Dutra and Bob Kennedy discuss scallop growth rings.
2. The Pocomo Seed scallops which were returned to the water within a few hours (n=35 on 9/15) are now doing about as well as the control group (n=215 on 9/15).

3., The Wauwinet "Nub" scallops (assumed to have resulted from a fall 2002 spawn) have spawned during the summer and are showing increased mortality in comparison to the control group. It is not known if this is due to them approaching the end of their normal life or if the extended exposure on the beach has reduced their ability to withstand the stress they face in the caged environment.
4. The Waiwinet Seed scallops are also showing greater mortality than the control group. Since their size distribution mirrors that of the control group, we would expect them to show the same survival rate. The increased mortality might be attributable to their 24 hour or more exposure on the beach in November, 2003.
5. All the caged scallops are under stress by barnacles and other life (sponge) growing on their shells. A portion of the wild scallops collected in the neighborhood of the study cages also show some signs of barnacles and other life on their shells. The lack of movement in the scallop pens probably contributes to the fouling on the scallop shells. The cages also are subject periodically to fouling, which reduces the water flow. We have scrubbed all of the 14 cages in April when the fouling became very severe.
A caged scallop has become fouled with barnacles and other growth.
One wild scallop has remained relatively free of barnacles. This one has a shell height of 67 mm.

 

27 July, 2004  
1. All four groups of scallops are statistically the same, and very close in size distribution to samples of the wild scallop population.

Measuring the size of the scallops.

2. There is no significant difference in overall survivability between the the rescued "nub" scallops and the other, younger scallops.
3. Group 3, the beached seed rescued from Pocomo, which had a significantly better survival rate than the other scallops is now more in line with the survival rate of the other groups.
4. The barnacles have stopped setting on the caged sacallops which have put on a centimeter of growth since the last barnacles have set.

 

12 June, 2004  
1. The control group grew an average of 6 mm since April 28. The beached scallops generally did not grow quite so fast.
Mean Size (mm)
Group 1
Group 2
Group 3
26 Nov, 2003
42.7
63.5

47.2
28 Apr, 2004
44.4
63.7
48.9
12 Jun, 2004
49.7
66.2
52.8
2. There is no significant difference in overall survivability between the beached scallops (74%) and the control group(73%).
3. Group 3, which was on beach only a couple of hours, seems to have a significantly better survival rate than those scallops which spent more time on the beach.
4. The scallops in the cages are strongly encrusted with barnacles.
30 April, 2004  
1. There has been no statistically significant growth since last November.
Mean Size (mm)
Group 1
Group 2
Group 3
26 Nov, 2003
42.7
63.5

47.2
28 Apr, 2004
44.4
63.7
48.9
2. We perhaps are beginning to see some effects of length of time on the beach. Group 3, which was on beach only a couple of hours, seems to be surviving better.
3. Apparently, one cause of scallop mortality is predation by small Black Claw Mud Crabs. The scallop traps have 1-inch mesh which excludes larger predators.

28 March, 2004

Please refer to the February 2004 presentation for more details of this ongoing study. We will be monitoring growth, survival rate, and spawing activity of these scallops throughout their lifetimes.

Scallop Survivorship Research Project Directed by Dr. Robert Knnnedy

Assisted by:
Dr. Peter B. Boyce, Research Associate and Treasurer, Maria Mitchell Association
Andrew W. McCandless, Senior, Nantucket High School
W. Forrest Kennedy, Senior, Cornell University
Valerie Hall, Science Faculty, Nantucket High School
Frank A. Dutra, Scalloper, Nantucket Shellfish Association

This project would not be possible without extensive local support from
the following organizations:

Nantucket Shellfish Association
Nantucket Harbor and Shellfish Advisory Board
Nantucket Sustainable Development Corporation
Town of Nantucket Marine and Coastal Resources Department
Nantucket Conservation Foundation
Wampanoag Hatchery, Martha’s Vineyard

Thanks to the following people for their help and assistance
(in alphabetic order):

Neil Cocker
Keith Conant
Bruce Cowan
Rhys Bender
Tracy Curley
Brian Donovan
Dave Fronzuto
 Rob Garrison
Matt Herr
Ken Kelley
Ron Shepherd
Christine Silverstein
Carl Sjolund
Douglas Smith

Last changed 09/27/04

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