update on scallop meat quality from rsa research · apicomplexan parasites at the aquatic...
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Update on scallop meat
quality from RSA research
CFF: Liese Siemann, Luisa Garcia, Samir Patel, and Ron Smolowitz
UM: Carl Huntsberger
RWU: Roxanna Smolowitz and Ava Mastrostefano
NOAA: Heather Haas
MAAS: Bob Prescott and Karen Dourdeville
• Goal is to examine the impact of biotic and abiotic factors on gray meat
prevalence and the likelihood of individual scallops having gray meats
• Five survey trips between August 2013 and March 2014 on the southern
portion of Georges Bank and fifteen survey trips between August 2015
and June 2017 on the northern portion of Georges Bank
• Meat quality was assessed based on a qualitative color scale with three
categories with colors ranging from white to brown to gray
• A subset of the collected meats were evaluated for the presence of
apicomplexan parasites at the Aquatic Diagnostic Laboratory at Roger
Williams University
Gray meat modeling
Total numbers of scallops assessed during each
survey month.Survey month and year Number of scallops sampled
September 2013 396
October 2013 380
December 2013 364
January 2014 363
March 2014 399
August 2015 411
September 2015 558
October 2015 557
November 2015 605
January 2016 563
March 2016 654
May 2016 641
June 2016 527
July 2016 530
October 2016 517
November 2016 385
January 2017 483
March 2017 520
May 2017 628
June 2017 502
9,983 scallops sampled
4.92% had gray or brown meats
Scallop relative abundance
• Gray meat prevalence at each station for each survey trip was modeled
using a quasibinomial distribution
• Meat quality of individual scallops, as gray meat presence (gray or brown)
or absence (white), was modeled using a binomial distribution
• Southern and northern stations were modeled separately due to the survey
area shift between 2014 and 2015
• Fixed effects used for modeling
• location (“easting” and “northing” in UTM space)
• bottom depth (29 – 106 m)
• bottom temperature (4 - 19°C)
• scallop density (0.38 - 640 bushels/km2)
• clapper ratio as proxy for natural mortality (0 - 2.0)
• scallop reproductive stage
• shell height
• area (Closed Area I, Closed Area II, open)
• downstream distance from a closed area (in a closed area, < 5 km from
a closed area, between 5 and 10 km from a closed area, or >10 km from
a closed area)
Selected models
Significant effects included
• location
• average shell height
• clapper ratio
• area (high in Closed Area I)
Southern Georges Bank 2013-2014
Northern Georges Bank 2015-2017
Significant effects included
• location
• bottom depth
• percentage of spent scallops
Significant effects included
• location
• shell height
• clapper ratio
• area (high in Closed Area I)
• scallop density
Gray meat prevalence Meat color/quality
Significant effects included
• scallop density
• shell height
• reproductive stage
Southern vs northern Georges Bank
Gray meats were more common when
• scallops were large (older)
• in areas with high natural mortality
• in a localized area (Closed Area I)
Northern Georges Bank
2015-2017
Southern Georges Bank
2013-2014
Gray meats were more common when
• scallops were spent
Suggests different causes for gray meats observed in these areas (and
years) – disease vs stress/energy depletion following spawning?
Relationship between meat color and severity of infection (assessed
using histological techniques) and presence of parasite (assessed using
PCR) is unclear
Apicomplexan parasite in discolored
meats from northern Georges Bank
Meat colorProtozoan
numberPCR +/-
White 0 Negative
Tan 0 Positive *
Tan 6 Negative *
Tan 9 Negative *
Brown 22 Positive
Brown 28 Positive
Brown 35 Positive
Gray 0 Positive *
Gray 3 Negative *
Gray 13 Positive
Gray 13 Positive
Gray 15 Positive
* Protozoan number vs PCR
detection of parasite don’t agree
Most recent data on gray meats on
Georges Bank (2017-2018)
Year Month Scallop
sampled Brown meat
Gray meat
Orange nodules
2017
August 873 5 2 1
September 782 3 1 0
October 777 13 2 2
December 754 7 4 1
2018
January 755 8 1 0
February 841 4 1 2
April 745 15 1 0
June 864 4 0 0
December had more gray
meats, and October and
April more brown meats
Orange nodules - mycobacteriumYear Month Scallops sampled
Orange Pustules
2013
September 396 8
October 380 5
December 364 4
2014 January 363 4
March 399 5
2015
August 411 4
September 558 0
October 557 4
November 605 5
2016
January 563 3
March 654 5
May 641 3
June 527 1
July 530 0
October 517 0
November 385 0
2017
January 483 0
March 520 0
May 628 0
June 502 1
Orange pustules (2013-2017)
Found in scallops from
stations where gray meats
were also prevalent
Grimm C, Huntsberger C, Markey K,
Inglis S, and Smolowitz R. 2016.
Identification of a Mycobacterium sp. as
the causative agent of orange nodular
lesions in the Atlantic sea scallop
Plactopecten magellanicus. Diseases of
Aquatic Organisms 118: 247 – 258
2016 2017 2018
Nematodes and TurtlesSince 2016, CFF has been taking
lavage samples from live turtles, and
gut content/fecal samples from dead
turtles that strand on Cape Cod. 16%
of all turtles have been positive for
nematodes.
Tagged Dead Tagged Dead
2016 22 28 6 1
2017 22 10 5 1
2018 35 33 7 4
Total 79 71 18 6
CCL mean ± SD (cm) 79.9 ± 9.6 81.4 ± 9.3
Total Turtles Positive NematodeYear
Turtles +Nematode
Microplastic?
S. sulcata egg
Nematodes and Turtles