In situ preda-on and behavioral plas-city of juvenile red king crabs (Paralithodes camtscha/cus) Benjamin Daly, Ginny Eckert, Allan Stoner, Tim White

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1 In situ preda-on and behavioral plas-city of juvenile red king crabs (Paralithodes camtscha/cus) Benjamin Daly, Ginny Eckert, Allan Stoner, Tim White

2 Red King Crab Low populacon abundance Know very liele about the ecology of juveniles PredaCon may create boeleneck limicng populacons NOAA-NMFS

3 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

4 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?

5 Tethering Study Lynn Canal Study Site Auke Bay Juneau Alaska

6 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

7 Tethering Study Effects of size and -me on survival Tethered crabs for 24 h in the field

8 Video cameras record predation ~10 m depth

9 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

10 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

11 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

12 Observed PredaCon Alaskan ronquil rock sole J. Pirtle kelp greenling Arctic shanny

13 Observed PredaCon

14 Predator species

15 In situ survival n= 32 n= 32 n= 32 n= 32 n=8, ANOVA

16 Times of mortal aeack

17 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.

18 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?

19 Lab PredaCon: predator exposure CondiConing Treatments Naïve (no predators) Limited Exposure (visual + chemical cues) Complete Exposure (visual + chemical + physical cues) Hippoglossus stenolepis Age mm total length

20 Lab PredaCon Experiment Mesocosm Island of substrate Fish pairs (halibut) 20 crabs (5 7.5 mm CL) halibut Length: 1 h Video recorded artificial substrate Crab survival Crab crypsis index: proporcon of crabs hiding

21 Crab Survival Repeated measures ANOVA p=0.038 n=6 n=6 n=6

22 Crab Crypsis Index

23 Diversity of predators. Conclusions PredaCon risk may be similar for several months postseelement. 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.

24 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

25 Questions?