Advances in king crab juvenile biology: Growth, life history, habitat, and predation

Transcription

1 Advances in king crab juvenile biology: Growth, life history, habitat, and predation Ginny L. Eckert University of Alaska Fairbanks, Juneau Center School of Fisheries and Ocean Sciences 1

2 Graduate Students Ben Daly PhD Fisheries in progress Jodi Pirtle PhD Fisheries 2010 Miranda Westphal MS Fisheries

3 Background Red King Crab Fishery 3

4 Bristol Bay Red King Crab Catch Total catch biomass (million lbs) Trawl bycatch Pot bycatch---males Cost recovery---u.s. Pot bycatch---females Retained---Foreign Retained---U.S. Handling mortality rate = 20% for pot & 80% for trawl Year NPFMC Crab SAFE 2010 Figure 2. Retained catch biomass and bycatch mortality biomass (million lbs) for Bristol Bay red king crab from 1960 to Handling mortality rates were assumed to be 0.2 for the directed pot fishery and 0.8 for the trawl fisheries. 4

5 Catch (1000 t) ret catch total directed catch (oberved discard) traw l bycatch total directed catch (model estimated discard) EBS Snow Crab Catch Survey Year Figure 1. Catch (1000 t) from the directed snow crab pot fishery and groundfish trawl bycatch. catch is retained catch plus discarded catch after 50% discard mortality was applied. Discard ca NPFMC Crab SAFE

6 EBS Chionoecetes bairdi Retained Male Catch Catch (1000T) Year US Retained Catch Russia Retained Catch Japan Retained Catch Total Retained Catch Figure 5. Eastern Bering Sea Chionoecetes bairdi retained male catch in the directed United States, Russian and Japanese fisheries, NPFMC Crab SAFE

7 Background Red King Crab Fishery Six of eight stocks closed to commercial fishing 7

8 Background Blue King Crab Fishery 8

9 Why have king crabs not recovered in the absence of fishing? Recruitment limitation Overfishing - threshold effects Climate-driven fluctuations Regime shift - Predation 9

10 King Crab Life Cycle Zoea 2 Zoea 3 Zoea 4 Zoea 1 Glaucothoe Mating Female with extruded eggs Crab Instar 1 10

11 Juvenile Production 11

12 Hatchery Culture: Juvenile Nursery What do juvenile red king crab eat? Reduce cannibalism Optimize growth Vary diet, density & substrate 12

13 C1-C3 Diet Density Substrate Diet*Density Diet Density Substrate Diet Density Substrate Diet*Density Daly et al Aquaculture 13

14 Color Experiment - add nutritional supplements Astaxanthin & Calcium 14

15 Color: Hue Hue Index Daly et al. in review 15

16 Survival Survival Daly et al. in review 16

17 Hatchery Culture: Juvenile Nursery Issues: Cannibalism Size grading -- diet & density 17

18 Survival Survival Size Grading Daly et al. in review 18

19 Survival Survival Size Grading Daly et al. in review 19

20 Hatchery Culture: Juvenile Nursery Increasing survival: Complex substrates: reduces antagonistic interactions 20

21 Hatchery Culture: Juvenile Nursery Increasing survival: Complex substrates: reduces antagonistic interactions Size grading: reduces cannibalism on smaller crabs 21

22 Hatchery Culture: Juvenile Nursery Increasing survival: Complex substrates: reduces antagonistic interactions Size grading: reduces cannibalism on smaller crabs Diet supplements: increases nutrition 22

23 Hatchery Culture: Juvenile Nursery Increasing survival: Complex substrates: reduces antagonistic interactions Size grading: reduces cannibalism on smaller crabs Diet supplements: increases nutrition Stocking density: decreases cannibalism 23

24 Hatchery Culture: Juvenile Nursery Increasing survival: Complex substrates: reduces antagonistic interactions Size grading: reduces cannibalism on smaller crabs Diet supplements: increases nutrition Stocking density: decreases cannibalism Increasing growth: Diet supplements: increases nutrition 24

25 Hatchery Culture: Juvenile Nursery Increasing survival: Complex substrates: reduces antagonistic interactions Size grading: reduces cannibalism on smaller crabs Diet supplements: increases nutrition Stocking density: decreases cannibalism Increasing growth: Diet supplements: increases nutrition Density dependent growth: moderate density has best growth 25

26 Juvenile Growth Studies Juvenile king crab growth during first year. Are hatchery animals similar to wild ones? 26

27 27

28 16 14 Crab Growth Hatchery crabs Wild crabs Carapace length (mm ± SD) C1 C2 C3 C4 C5 C6 C7 C8 C9 Molt stage Westphal et al. in prep 28

29 29

30 Carapace length (mm ± SD) a. * Hatchery crabs Wild crabs Field crabs * * * Comparisons 2 with wild b. Hatchery crabs Wild crabs Field crabs * * crabs Spine length (mm ± SD) * * * January February March April May June July August Westphal et al. in prep 30

31 Juvenile Production 31

32 Nursery Habitat Function Nursery habitats should maximize survival and growth Complex benthic habitat is important Why is structure important? Are certain habitats more valuable? What is the role of structure in survival? 32

33 <7 Habitat selection ;7!='++3)&'#$ >'&?(3)&'#$ 0$$*12'%2*.$3456 : ! 7 )*##+(,(##+( -&'."+(!'./!"#$%&'%( Pirtle & Stoner 2010 JEMBE!! 33

34 Algae Algae Mimic Fouled Algae Mimic Experimental Substrata Bryozoan Hydroid Bryozoan Mimic Hydroid Mimic Fouled Bryoz Mimic Fouled Hydro Mimic 34

35 Competency of Hatchery Juveniles Lab Predation Role of habitat Sand Hydroids Hydroids/Macroalgae Hydroid Mimics Pirtle et al. in prep 35

36 Habitat preferences in absence of predator : (*"+,-.,&/0,"1123$"%$2+1, # # 5 " & '(!( ')!!!"#$%"% Pirtle et al. in review MEPS 36

37 Predation by cod in different habitats =; =: " (*"+,-.,&/0,12"#3,14+356*7, =9 =8 < ; : # # # # 9 8 & '(!( ')!!!"#$%"% Pirtle et al. in! review MEPS 37

38 38

39 Laboratory Predation Conclusions Structure increases survival with fish predators Prefer biogenic habitats when predators are absent Engage in refuge-seeking behavior when predators are present 39

40 40

41 % survival visual complete exposure to exposure to predators predators Daly et al. in prep. 41

42 Laboratory Predation Conclusions Structure increases survival with fish predators Prefer biogenic habitats when predators are absent Engage in refuge-seeking behavior when predators are present Predator defense learned. 42

43 Crab Tethering Methods 43

44 44

45 45

46 5 m 5 m 46

47 47

48 48

49 49

50 50

51 51

52 Habitat Treatments Procedural Control Structure No Structure 52

53 Potential Predators Observed Pacific cod Arctic shanny Walleye pollock Northern ronquil Kelp greenling Alaskan ronquil Whitespotted greenling Decorated warbonnet Dusky rockfish Crescent gunnel Quillback rockfish English sole Copper rockfish Yellowfin sole Sculpins Starry flounder Buffalo sculpin Giant Pacific octopus Great sculpin Hermit crabs Crested sculpin Helmet crab Silverspotted sculpin Decorator crab Red Irish lord Red king crab Sturgeon poacher Pycnopodia seastar 53

54 Observed in Video Pacific cod Arctic shanny Walleye pollock Northern ronquil Kelp greenling Alaskan ronquil Whitespotted greenling Decorated warbonnet Dusky rockfish Crescent gunnel Quillback rockfish English sole Copper rockfish Yellowfin sole Sculpins Starry flounder Buffalo sculpin Giant Pacific octopus Great sculpin Hermit crabs Crested sculpin Helmet crab Silverspotted sculpin Decorator crab Red Irish lord Red king crab Sturgeon poacher Pycnopodia seastar 54

55 Observed Predation Pacific cod Arctic shanny Walleye pollock Northern ronquil Kelp greenling Alaskan ronquil Whitespotted greenling Decorated warbonnet Dusky rockfish Crescent gunnel Quillback rockfish English sole Copper rockfish Yellowfin sole Sculpins Starry flounder Buffalo sculpin Giant Pacific octopus Great sculpin Hermit crabs Crested sculpin Helmet crab Silverspotted sculpin Decorator crab Red Irish lord Red king crab Sturgeon poacher Pycnopodia seastar 55

56 Alaskan ronquil Sculpins Observed Predation Buffalo sculpin Pycnopodia Seastars 56

57 Crab Field Survival No Structure Structure Control Structure p < Stage p = 0.07 Crab survival (%) Age-0 Age-1 Crab Stage Pirtle et al. in review 57

58 58

59 Field Predation Conclusions Structure increases survival with a variety of predators in the field Structure, cryptic behavior, and direct defense improve survival in the field Role of groundfish predation is questionable 59

60 Why have king crabs not recovered in the absence of fishing? Recruitment limitation Overfishing - threshold effects Climate-driven fluctuations Regime shift - Predation 60

61 Blue King Crab 61

62 Future Studies Fish predation - Gut content analysis Habitat studies Larval & juvenile king crab recruitment in Bristol Bay Blue king crab 62

63 Thanks to AKCRRAB supporters! 63