In situ predation and behavioral plasticity of juvenile red king crabs

In situ predation and behavioral plasticity of juvenile red king crabs

In
situ
preda-on
and
behavioral
plas-city
of
juvenile
red
king
crabs
(Paralithodes
camtscha/cus)
Benjamin Daly, Ginny Eckert, Allan Stoner, Tim White Red King Crab •  Low populaCon abundance •  Know very liEle about the ecology of juveniles •  PredaCon may create boEleneck limiCng populaCons NOAA-NMFS
Juvenile Red King Crab •  Nearshore nursery habitats •  Predator defenses: crypsis, spines •  Gut content analysis: Pacific cod consume large soM‐shell RKC, P. cod significant predators of Tanner crabs, observaCons outside shallow nearshore areas •  InformaCon on early benthic phase RKC is lacking in nearshore areas Research ObjecCves 1.
Look
at
in
situ
preda-on
of
recently
se>led
RKC
•  Does body size during the first juvenile stages influence predaCon suscepCbility? •  What are the major predator groups? Tethering Study Lynn Canal
Study Site
Auke Bay
Juneau
Alaska
Tethering Studies •  Common in benthic marine studies (e.g., crab, lobsters) •  Useful for understanding rela-ve predaCon rates •  This work is expanding on previous RKC tethering studies in southeast AK (Pirtle et al., 2012) NOAA-NMFS
Tethering Study Effects of size and -me
on survival •  Tethered crabs for 24 h in the field Video cameras record
predation
~10 m depth
PotenCal Predators Pacific cod Walleye pollock Kelp greenling WhitespoEed greenling Undefined rockfish Buffalo sculpin Great sculpin Crested sculpin SilverspoEed sculpin Red Irish lord Undefined sculpins Sturgeon poacher ArcCc shanny Northern ronquil Alaskan ronquil Starry flounder Yellowfin sole Northern rock sole Crescent gunnel Giant Pacific octopus Red king crab Graceful kelp crab Undefined hermit crabs Undefined Shrimps Tubesnout Wolf eel Sunflower star Observed in Video Pacific cod Walleye pollock Kelp greenling WhitespoEed greenling Undefined rockfish Buffalo sculpin Great sculpin Crested sculpin SilverspoEed sculpin Red Irish lord Undefined sculpins Sturgeon poacher ArcCc shanny Northern ronquil Alaskan ronquil Starry flounder Yellowfin sole Northern rock sole Crescent gunnel Giant Pacific octopus Red king crab Graceful kelp crab Undefined hermit crabs Undefined Shrimps Tubesnout Wolf eel Sunflower star Observed Predators Pacific cod Walleye pollock Kelp greenling WhitespoEed greenling Undefined rockfish Buffalo sculpin Great sculpin Crested sculpin SilverspoEed sculpin Red Irish lord Undefined sculpins Sturgeon poacher ArcCc shanny Northern ronquil Alaskan ronquil Starry flounder Yellowfin sole Northern rock sole Crescent gunnel Giant Pacific octopus Red king crab Graceful kelp crab Undefined hermit crabs Undefined Shrimps Tubesnout Wolf eel Sunflower star Observed PredaCon Alaskan ronquil
rock sole
J. Pirtle
kelp greenling
Arctic shanny
Observed PredaCon Predator species In situ survival n= 32
n=8, ANOVA
n= 32
n= 32
n= 32
Times of mortal aEack Conclusions •  Crabs were consumed by a diverse group of predators. •  Pacific cod showed liEle interest in crabs. •  PredaCon on early benthic phase red king crabs may be significant during molCng. •  Differences in predaCon suscepCbility may be ecologically inconsequenCal during the first juvenile stages. •  Crabs consumed primarily in daylight hours. Research ObjecCves 1.
Look
at
in
situ
preda-on
of
recently
se>led
RKC
2.
Inves-gate
RKC
predator
responses
•  Do predator responses improve with experience? Lab PredaCon: predator exposure CondiConing Treatments •  Naïve (no predators) •  Limited Exposure (visual + chemical cues) •  Complete Exposure (visual + chemical + physical cues) Hippoglossus stenolepis
Age-1 185 mm total length
Lab PredaCon Experiment Mesocosm
•  Island of substrate •  Fish pairs (halibut) •  20 crabs (5‐7.5 mm CL) Length: 1 h Video recorded Crab
survival
Crab
crypsis
index:
proporCon of crabs hiding halibut
artificial substrate
Crab Survival Repeated measures ANOVA
p=0.038
n=6
n=6
n=6
Crab Crypsis Index Conclusions •  Diversity of predators. •  PredaCon risk may be similar for several months post‐
seElement. •  Predator responses can be improved with experience. •  RKC see/smell predators, but physical interacCons are important to iniCate enhanced avoidance responses. •  More informaCon is needed on predator avoidance behavior and predaCon in the field to evaluate if juvenile predaCon limits red king crab populaCons. •  Future studies should examine temporal and spaCal variaCon in predaCon pressure. Acknowledgements NOAA ‐ Fisheries Behavioral Ecology Program, HMSC, Newport OR –  Dr. C. Ryer, C. Magel , S. Haines M. OEmar AluCiq Pride Shellfish Hatchery –  J. Swingle, J. Hetrick University of Alaska Fairbanks –  J. Pirtle, J. Sylvan University of Alaska Southeast –  REU program Funding by Sea Grant Aquaculture Questions?