advancement of sunray venus culture macrocallistanimbosa...
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Advancement of
Sunray Venus Culture
Macrocallista nimbosa
through Evaluation of Alternative
Growout and Harvesting Methods
Leslie N. Sturmer, Todd Osborne, William WhiteUniversity of Florida IFAS
Rex EllisSt. Johns River Water Management District
Sunray Venus Clam
Culture in Florida
Eight Years of Research
and Development
Bottom bags (4’ x 4’, 16 ft2) made of 9 mm polyester mesh material
Evaluation of Growout Methods: Bottom Bag• Standard hard clam culture
methods used as a starting point − In Florida, the typical culture
method is the bottom bag• Results were not consistent,
2007-9 − Survivals ranging from 24-76%− Site and substrate-dependent
• Shell deformities or irregularities observed of sunray venus in bags− Observations ranging from
8-48% per bag in early trials Limited to ventral margin with one valve having excessive curvature resulting in a depression
Broadcasted seed covered with 9 mm mesh polyester netting edged with lead line and additional layer of plastic netting
staked with PVC pipe
Evaluation of Growout Methods: Bottom Plant• Preliminary evaluation of bottom plants
as a culture method, 2009-10 − Good survival− Faster growth than bottom bags− Shell deformities <2%
• Special lease provisions limit use of mechanical harvesting on shellfish aquaculture leases
• Growers restricted to use of hand tools (e.g., rake) to harvest bottom-planted sunray venus clams
Project Objectives1) Eliminate barriers to commercial production
of a promising new aquaculture species by utilizing alternative culture and harvest methods− Document production and product quality
characteristics of two culture methods 2) Compare effects of harvesting bottom-planted
sunray venus clams with a mechanical harvesting device versus those associated with harvesting bottom bags− Document water quality and soil properties
associated with two harvest methods
Funded by Florida Department of Agriculture and Consumer Services, Florida Aquaculture Grant Program, 2013-14
• Treatments − Bottom plants, 9 mm polyester mesh netting,
½” mesh HDPE cover netting, 8’ x 10’, 80 ft2
− Bottom bags (16 ft2), belt of 5, 80 ft2 per row• Replication, n=4• Stocking density, 55/ft2
• Seed size, 15-20 mm SL• Site, UF lease, Cedar Key, FL• Plant, November 2012• Harvest, ~12 months later, 2013
Growout Methods
• Mechanical harvesting device, “box” harvester used in Virginia− SS box-shaped− 5 hp pump delivers pressurized
water via nozzles along spray bar− No tines, angle of box digs into
substrate− Wire basket collects clams
Harvest Methods
Sampling Design
• Before-After, Control-Impact, Paired (BACIP)
– Establish baseline prior to planting or harvesting
• Control sites– Direct comparison of culture
and harvest methods • Experimental sites
– Differentiate natural changes from those caused by harvesting
• Reference sites
• Survival the same for both culture methods• Bottom-planted sunray venus were
− 29% larger in shell length (p<0.0001)− 76% heavier in total weight p<0.0001)− 60% more meat weight (wet) (p=0.0023)− 80% increase in yield (lb/16ft2) (p=0.0126)
Production Characteristics
48.4 48.1
17.3
4.7
16.7
47.4
61.9
29.9
8.3
28.2
0
10
20
30
40
50
60
70
Survival (%) Length (mm) Weight (g) Meat Wt (g) Yield (lb/16 ft2)
Bottom Bags Bottom Plant
• Grit evaluation, 5-point scale where 0=no grit and 4=extremely gritty− At harvest, sunray venus were rated as
“slightly to moderately” gritty − After 24 hours of purging, 70% reduction in
grit for clams harvested by both methods− After 48 hours, values same for both methods
• Shell deformities (p=0.01)
− 3.1 + 0.9%, bottom bags− 0.5 + 1.0%, bottom plant
• Shell breakage (p=0.12)
− 0.5 + 0.4%, bottom bags− 2.9 + 2.2%, bottom plant
• Shelf life, 10 days− 100%, both culture
methods
Product Quality Characteristics
1.3
0.4 0.3
1.7
0.50.3
0
0.5
1
1.5
2
2.5
0-Hours 24-Hours 48-HoursPurge Time
Grittiness (0-4 Scale)
Bottom Bags Bottom Plant
• Nine sondes (YSI 6600) deployed − 5’ in cardinal directions from
both bag and bottom plants − One sonde placed mid-way between
culture unit replicates− Additional sondes placed 25’
down current of both culture units
Effects of Harvest Methods on Water Quality
MID
5 ftBot.
Plant
20 ft
5 ft
5 ft
5 ft
5 ft
N-BP-5
W-BP-5 E-BB-5
S-BP-5
BP-25
Bags
5 ft
5 ft
20 ft
N-BB-5
BB-25
S-BB-5
5 ft
N• Multiple parameters measured
continuously (every minute) for 48 hours pre- and post-harvest− Water temperature− Salinity− Dissolved oxygen− Turbidity
• Turbidity (resuspension of small soil particles into water column) was greatest concern and showed noticeable differences− Intensity: Maximum values and
max mean values of sondeswith highest detected turbidity
− Duration: Time required to return to corrected background conditions (30 min pre-harvest)
• Each harvest replicate treated as an independent evaluation as ambient conditions (tide, current, wind, back-ground turbidity) differed
Effects of Harvest Methods on Turbidity
Rep 1 - 23 Oct 2013
Rep 2 - 18 Nov 2013
Rep 3 - 3 Dec 2013
Rep 4 - 16 Dec 2013
-48 hrs
+24 hrs
+48 hrs
-24 hrs
0 hrs
Turb
idity
(NTU
)Tu
rbid
ity (N
TU)
Turb
idity
(NTU
)Tu
rbid
ity (N
TU)
Intensity
Duration
Comparison of highest mean turbidity values for harvest methods with 30 min pre- and post-harvest values
Effects of Harvest Methods on Turbidity (NTU)
60.5 b74.5 ab
99.8 a
81.8 ab
0
20
40
60
80
100
120
30 min Pre Bottom Bag Bottom Plant 30 min Post
Replicate 1
Data were analyzed using General Linear Model analysis with Tukey’s post-hoc test in SAS Software
30.3 b
60.7 a
37.2 b30.9 b
0
20
40
60
80
100
120
30 min Pre Bottom Bag Bottom Plant 30 min Post
Replicate 2
31.9 b41.0 a
49.0 a 49.0 a
0
20
40
60
80
100
120
30 min Pre Bottom Bag Bottom Plant 30 min Post
Replicate 3
16.5 b
65.6 a
52.7 a
23.0 b
0
20
40
60
80
100
120
30 min Pre Bottom Bag Bottom Plant 30 min Post
Replicate 4
• Replicate 1 – Outgoing tide, winds light (6-10 knots) out of north, following falling tide• Turbidity associated with harvesting bags returned to background levels in 2 minutes,
and in 5 minutes with pump harvester
Effects of Harvest Methods on Turbidity
Rep 1 Sonde S-BP-5
Rep 1 Sonde S-BB-5Bags Harvested
(upstream)
Bags Harvested
Pump Driven Harvester
Time on 23-Oct-13
Comparison of bag harvest duration (top graph) and pump-driven harvester (bottom graph)
• Replicate 2 – Incoming tide from S to N, winds (3-5 knots) out of sout• Return interval for bag harvest not determined as it was greater than time between
harvest activities, return to background for pump-driven harvester was 9 minutes
Effects of Harvest Methods on Turbidity
Rep 2 Sonde N-BP-5
Bags Harvested
Pump Driven Harvester
Bags Harvested (upstream)
Rep 2 Sonde N-BB-5
Time on 18-Nov-13
Comparison of bag harvest duration (top graph) and pump-driven harvester (bottom graph)
• Commercial-scale trial, 17 June 2014− Unfarmed area of 300 ft2 (25’ by 12’ plot)
• Eleven sondes deployed − 5’ and 25’ in cardinal directions from
mid-points of test plot − 45’ to south of plot with one sonde located
at mid-point of plot and two located 20’ to east and west
• Turbidity measured every minute for 24 hours pre- and post-harvest
Effects of Pump-driven Harvest on Turbidity
N-25
Mock Harvest
Area
20 ft
20 ft
20 ft20 ft
20 ft20 ft
5 ft
5 ft5 ft
5 ft
20 ft
N-5
W-25 W-5 E-25E-5
S-5
S-25
SW-45 S-45 SE-45
Effects of Pump-Harvester on TurbidityComparison of sondes located 5’ from harvest area over 30 min pre- and post-harvest
• Maximum turbidity values per harvest set ranged from 62 to 98 NTU• Return to baseline levels (19.1+2.6 NTU) was within 3 min after first harvest set,
immediately after second set, took longer after third set (7 min) due to tidal change
Effects of Pump-Harvester on TurbidityComparison of sondes located 25’ from harvest area 30 min pre- and post-harvest
• Maximum turbidity values per harvest set ranged from 24 to 60 NTU• Return to baseline levels (13.1+1.4 NTU) was within 2-10 minutes
Effects of Pump-Harvester on TurbidityComparison of sondes located 45’ from harvest area 30 min pre- and post-harvest
• Maximum turbidity values in first and second harvest set were 25 and 52 NTU• Return to baseline levels (17.8+0.9 NTU) was within 6 min after first harvest set,
with little to no change during or after second and third sets as values returned to baseline during harvest
0
40
80
120
160
11:1016-Jun
17:1016-Jun
23:1016-Jun
5:1017-Jun
11:1017-Jun
17:1017-Jun
23:1017-Jun
5:1018-Jun
11:1018-Jun
Turb
idit
y (N
TU
)
North South East WestSonde Locations (5’ from Harvest Area):
Harvest
Effects of Pump-Harvester on Turbidity
• A weather event was captured 14 hours post-harvest (1:10 am) with wind speeds gusting to 26 knots out of ESE (wind direction which most influences test area)
• Maximum turbidity recorded at all sondes ranged from 123 to 155 NTU• Duration (4.5 hrs) and wind effect had greater influence on turbidity than harvester
Comparison of sondes located 5’ from harvest area 24 hours pre- and post-harvest
Effects of Harvest Methods on Soil Properties
• Soil cores collected (n=3)− Prior to planting to establish
baselines − At harvest (week 0) per culture
replicate to compare effects of harvest methods
− At reference (unfarmed) sites to compare with baseline and harvest methods
− At 4 and 8 weeks to evaluate changes over time
• Soil samples analyzed for particle size distribution− Sand− Fines (clay + silt)− Organic matter
Effects of Harvest Methods on Soil Properties• Sand and fines content
differed significantly between plant and harvest− Variation minimal over year− Sands increased 97-98% − Fines decreased 3 to 2.3%
• At harvest and 4 weeks post-harvest, sand and fines were similar at all sites
• At 8 weeks, sand was higher and fines lower at bottom bag sites in comparison to bottom plant and reference sites
• Over time, sand content significantly decreased and fines content significantly increased at bottom plant and reference sites
85
88
91
94
97
100
Plant Harvest - Wk0 Harvest - Wk4 Harvest - Wk8
Sand
(%)
Reference Bottom Bag Bottom Plant
0
2
4
6
8
10
Plant Harvest - Wk0 Harvest - Wk4 Harvest - Wk8
Fine
s (%
)
Recovery of Harvest Tracks
• Cross-sectional soil elevation profiles were monitored to capture harvest tracks and recovery– PVC pipe arrays pushed
into the substrate perpendicular to harvest sites
• 3-6 pipes located in harvest area
• Reference pipes on each end of the array placed outside harvest area
– Distances from bottom substrate to top of the frame at each pipe measured at weeks 0, 4, and 8
– Differences in elevation at week 0 to reference values reflected effects of culture/harvest methods
– Differences in subsequent weeks reflected soil infill or loss over time
• Soil elevations of harvest tracks standardized to reference conditions (“ground 0”) • At harvest, sediments were mounded at bag sites while a track depth of -3.7 cm was created
by the harvester. By week 4, adjacent bottom bag sites appeared to have supplied sediments to fill in harvester tracks. By week 8, both recovered to levels similar to reference conditions.
• Soil elevations significantly differed between harvest sites at each sampling period; differences were only ~7.5 cm at week 0 and <1 cm by week 8.
3.8
0.3
-0.9
-3.7
-1.8 -1.6
-5
-2.5
0
2.5
5
Harvest - Wk0 Harvest - Wk4 Harvest - Wk8
Soil
Elev
atio
n (c
m)
Bottom Bag Bottom Plant
Recovery of Harvest Tracks
0
Summary
Sunray venus production was increased by 80% using the bottom plant method versus bottom bags
Culture period to reach market size (~50 mm SL) could be reduced by 15-20% (1.8-2.5 months) using bottom plant method, which lessens risks associated with mortality
Product quality of sunray venusharvested from bottom plants was not compromised
Summary
Turbidity values either did not differ between harvest methods or were higher during the bag harvest and natural events compared to the pump-driven harvester
Impacts to water column were short term as turbidity values returned to background levels within 5-9 minutes
Consistent changes in the soils suggested that natural processes were more active in sorting particle size than were harvest methods
Summary • Physical effects of mechanical shell-
fish harvesters are reported in the literature to be short-lived with rate of recovery varying among study sites
• To determine extent and duration of potential impacts of mechanical harvesting in Florida, a pump-driven harvester was tested under actual lease conditions
• Science-based information was provided to FDACS to address statutory or regulatory barriers to allow for this harvesting activity
Questions?
For more infomaton, contact Leslie Sturmer, LNST@ufl.edu, or visit http://shellfish.ifas.ufl.edu
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