Red king crab Snow crab
Developing procedures for processing the gastric mill of red king crab and snow crab for estimation of band counts April
1,2 Rebert *,
Joel
1 Webb ,
Kevin
1 McNeel ,
and Gordon
2 Kruse
1Alaska
Department of Fish and Game, Division of Commercial Fisheries 2University of Alaska Fairbanks, College of Fisheries and Ocean Sciences
Rationale • • •
•
•
Readability Codes
Age information is essential for fisheries management in Alaska. There is currently no reliable age determination method for commercially important crab in Alaska.
Clarity of banding pattern
Range of band count
Clear banding
+/- 0-2 bands
Results Clarity
80%
clear
unclear
60%
40%
Banding patterns potentially indicative of growth variability have been observed in thin sections of eye stalks and gastric mill ossicles in Alaska red king crab and snow crab.
Fairly clear banding
Exploring the presence and clarity of banding patterns throughout the structures of the gastric mill and eye stalks is necessary for developing and standardizing speciesspecific procedures.
20%
+/- 3-5 bands
0% Eyestalk
Mesocardiac Pterocardiac
Robust age determination would improve stock assessment and could decrease uncertainty in setting overfishing limits for management of Alaska crab stocks.
low +/- >5 bands
Eyestalk
Mesocardiac Pterocardiac
Red King Crab Range
80%
Vague banding
Zygocardiac
Zygocardiac
Snow Crab
high
60%
40%
No visible banding
estimate low
20%
0%
Objective
Eyestalk
Structure compromised
Identify one structure as preferred for estimating band counts by identifying structures containing the highest proportion of clear banding patterns and precise band counts for red king crab and snow crab.
n= 209
estimate high
left
right
Mesocardiac Pterocardiac
n= 91
n= 42 Snow Crab n= 51
Zygocardiac n= 60
Snow crab
•
The pterocardiac contained the highest proportion of sections with clear banding and lowest band range for snow crab.
•
The zygocardiac contained the highest proportion of sections with clear banding and lowest band range for red king crab.
•
The zygocardiac contained sections with the best readability overall for both species.
Discussion and Conclusion uromesocardiac
•
Banding patterns were found in all structures, but clarity and range of band count differed.
•
Based on these results, we recommend using the zygocardiac for further investigation of banding significance in red king and snow crab as potential age structures.
•
The banding patterns we found share similarities to growth patterns observed in other fish age structures; however, they are complex and development of criteria is necessary.
eyestalk
uromesocardiac pterocardiacs
Hard structures were cleaned and isolated, and embedded in resin.
n= 379
Eyestalk
pterocardiac
zygocardiacs
Crabs were captured and euthanized by freezing. Stomachs and paired eyestalks were removed from each individual.
n=Red 96 King Crab n= 140
Zygocardiac
Red king crab
Methods eyestalks
Mesocardiac Pterocardiac
zygocardiac
Structures were thin-sectioned (180 µm) from the proximal end.
Each thin section was evaluated for clarity and band count using “Readability Codes.” Readability Codes.
*Corresponding Author:
[email protected]
1,2 Rebert *,
Joel
1 Webb ,
Kevin
1 McNeel ,
and Gordon
2 Kruse
1Alaska
Department of Fish and Game, Division of Commercial Fisheries 2University of Alaska Fairbanks, College of Fisheries and Ocean Sciences
Rationale • • •
•
•
Readability Codes
Age information is essential for fisheries management in Alaska. There is currently no reliable age determination method for commercially important crab in Alaska.
Clarity of banding pattern
Range of band count
Clear banding
+/- 0-2 bands
Results Clarity
80%
clear
unclear
60%
40%
Banding patterns potentially indicative of growth variability have been observed in thin sections of eye stalks and gastric mill ossicles in Alaska red king crab and snow crab.
Fairly clear banding
Exploring the presence and clarity of banding patterns throughout the structures of the gastric mill and eye stalks is necessary for developing and standardizing speciesspecific procedures.
20%
+/- 3-5 bands
0% Eyestalk
Mesocardiac Pterocardiac
Robust age determination would improve stock assessment and could decrease uncertainty in setting overfishing limits for management of Alaska crab stocks.
low +/- >5 bands
Eyestalk
Mesocardiac Pterocardiac
Red King Crab Range
80%
Vague banding
Zygocardiac
Zygocardiac
Snow Crab
high
60%
40%
No visible banding
estimate low
20%
0%
Objective
Eyestalk
Structure compromised
Identify one structure as preferred for estimating band counts by identifying structures containing the highest proportion of clear banding patterns and precise band counts for red king crab and snow crab.
n= 209
estimate high
left
right
Mesocardiac Pterocardiac
n= 91
n= 42 Snow Crab n= 51
Zygocardiac n= 60
Snow crab
•
The pterocardiac contained the highest proportion of sections with clear banding and lowest band range for snow crab.
•
The zygocardiac contained the highest proportion of sections with clear banding and lowest band range for red king crab.
•
The zygocardiac contained sections with the best readability overall for both species.
Discussion and Conclusion uromesocardiac
•
Banding patterns were found in all structures, but clarity and range of band count differed.
•
Based on these results, we recommend using the zygocardiac for further investigation of banding significance in red king and snow crab as potential age structures.
•
The banding patterns we found share similarities to growth patterns observed in other fish age structures; however, they are complex and development of criteria is necessary.
eyestalk
uromesocardiac pterocardiacs
Hard structures were cleaned and isolated, and embedded in resin.
n= 379
Eyestalk
pterocardiac
zygocardiacs
Crabs were captured and euthanized by freezing. Stomachs and paired eyestalks were removed from each individual.
n=Red 96 King Crab n= 140
Zygocardiac
Red king crab
Methods eyestalks
Mesocardiac Pterocardiac
zygocardiac
Structures were thin-sectioned (180 µm) from the proximal end.
Each thin section was evaluated for clarity and band count using “Readability Codes.” Readability Codes.
*Corresponding Author:
[email protected]
