Advances in King Crab Juvenile Biology: Growth, Life History, Habitat, and Predation Ginny L

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 Graduate Students

Ben Daly PhD Fisheries in progress Jodi Pirtle PhD Fisheries 2010

Miranda Westphal MS Fisheries 2011

2 Background – Red King Crab Fishery

3 BSAI Crab SAFE Bristol Bay Red King Crab

140

Trawl bycatch Bristol Bay Pot bycatch---males 120 Cost recovery---U.S. Pot bycatch---females Red King Crab Retained---Foreign Retained---U.S. Catch 100

80 Handling mortality rate = 20% for pot & 80% for trawl

60 Total catch biomass (million lbs) lbs) (million biomass catch Total 40

0 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998 2003 2008 Year

Figure 2. Retained catch biomass and bycatch mortality biomass (million lbs) for Bristol Bay red king NPFMC Crab SAFE 2010 crab from 1960 to 2009. Handling mortality rates were assumed to be 0.2 for the directed pot fishery and 0.8 for the trawl fisheries. 4

September 2010 157 BSAI Crab SAFE EBS Snow Crab

ret catch 200 total directed catch (oberved discard) traw l bycatch total directed catch (model estimated discard) 180

160 EBS 140 Snow Crab Catch 120

100

80 Catch (1000 t) Catch(1000

0 1975 1980 1985 1990 1995 2000 2005 2010 2015 Survey Year

Figure 1. Catch (1000 t) from the directed snow crab pot fishery and groundfish trawl bycatch. Total catch is retained catch plus discarded catch after 50% discard mortalityNPFMC was Crab applied. SAFE Discard 2010 catch was estimated from observer data 1992 to present. Discard for 1978 to 1991 was estimated in the model. 5 Trawl bycatch is male and female bycatch from groundfish trawl fisheries with 80% mortality applied.

exploitation rate 0.0 0.2 0.4 0.6 0.8 1.0 1.2

1980 1985 1990 1995 2000 2005

Survey Year

Figure 2. Exploitation rate estimated as the preseason GHL divided by the survey estimate of large male biomass (>101 mm) at the time the survey occurs (dotted line). The solid line is the retained catch divided by the survey estimate of large male biomass at the time the fishery occurs. Year is the survey year.

September 2010 75 BSAI Crab SAFE EBS Tanner Crab

EBS Chionoecetes bairdi Retained Male Catch

20 Catch (1000T) 10

0 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year

US Retained Catch Japan Retained Catch Russia Retained Catch Total Retained Catch

Figure 5. Eastern Bering Sea Chionoecetes bairdi retained male catch in the directed United States, Russian and Japanese fisheries, 1965-2010. NPFMC Crab SAFE 2010

EBS Chionoecetes bairdi Mature & Legal Male Biomass

300 150

250

200 100

150

100 50 LMB (1000T) MMB (1000T) MMB

0 0 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year

MMB @ Survey MMB @ Mating LMB @ Survey LMB @ Mating

Figure 6. Eastern Bering Sea C. bairdi mature and legal male biomass at time of the survey and mating, 1965-2010. (2010/11 MMB and LMB at time of mating not estimable absent 2010/11 catch data).

September 2010 307 Background – Red King Crab Fishery

Six of eight stocks closed to commercial fishing

7 Background – Blue King Crab Fishery

8 Why have king crabs not recovered in the absence of fishing?

• Recruitment limitation

• Overfishing - threshold effects

•Climate-driven fluctuations

• Regime shift - Predation

9 King Crab Life Cycle

Zoea 3 Zoea 4 Zoea 2

Zoea 1 Glaucothoe Mating

Female with extruded eggs Crab Instar 1

10 Juvenile Production

11 Hatchery Culture: Juvenile Nursery

What do juvenile red king crab eat? Reduce cannibalism Optimize growth Vary diet, density & substrate

12 Author's personal copy

B. Daly et al. / Aquaculture 293 (2009) 68–73 71 C1-C3

Diet Density Substrate Diet*Density

Diet Density Substrate

Diet Density Substrate Diet*Density

Daly et al. 2009 Aquaculture Fig. 1. Mean±SE of A) survival, B) carapace width, and C) wet weight of red king crab juveniles reared using Cyclop-eeze®, Zeigler™ shrimp nursery feed, and frozen enriched 13 Artemia as diets at stocking densities of 500 m− 2,1000m− 2, and 2000 m− 2 with and without artiﬁcial substrate.

3.1.3. Substrate use substrate compared to when reared in the presence of substrate (42.9± In silos containing substrate, more crabs were found in the sub- 8.0 mg, 3.4±0.17 mm) (Table 2, Fig. 2B, C). strate (59.0±1.8%) than on the bottom (41.0±1.8%, df =26, t=5.00, pb0.001). Within the substrate, higher abundances of crabs were 3.2.3. Substrate use observed on artificial seaweed (47.6±2.1%) than gillnet (24.7±2.1%, In silos containing substrate, more crabs were found in the sub- Tukey, p b0.001) and mechanical biofilter (20.9±1.8%, Tukey, strate (63.4±2.6%) than on the bottom (36.6±2.7%, df=14, t=6.87, pb0.001). For each substrate type, there were no differences in substrate pb0.001). Within the substrate, higher abundances of crabs were use among diet or stocking density treatments (ANOVA p=0.757). observed on artificial seaweed (63.2±5.4%) than gillnet (34.1±5.3%, df=14, t=3.84, p=0.002). No differences in substrate use were seen 3.2. Experiment 2: C3–C6 among stocking density treatments (ANOVA p=0.735).

3.2.1. Survival 4. Discussion Average (±SE) survival from C3 to C6 in all treatments was 38± 5.6%. The highest survival of 75.5% was observed in an individual Our results demonstrate that diet, stocking density and substrate replicate stocked at 800 m− 2 with substrate. Crabs had a higher significantly impact survival and growth of juvenile red king crab. survival when reared at a stocking density of 800 m− 2 (48.7±8%), Improved hatchery rearing technology and superior husbandry techni- compared to 1600 m− 2 (28.5±6.6%) (Table 2, Fig. 2A). Overall, silos ques can lead to successful red king crab rearing. Optimal rearing con- with substrate had higher survival (58.7±4.8%) than those without ditions for juvenile red king crab likely consist of a mixed diet with substrate (19.6±3.2%) (Table 2, Fig. 2A). artificial substrate at intermediate stocking densities. The specific nutritional requirements of juvenile red king crab are 3.2.2. Growth unknown, and as a result commercial crustacean feeds are not spe- By day 44, crabs were a mixture of C4s, C5s, and C6s and weighed cifically formulated for red king crab. Therefore, our experiments had 69.4±9.3 mg and were 4.0±0.21 mm in CW. Crabs reared at 800 m−2 the goal of determining which commercially-available and hatchery- were not different in wet weight or CW from those reared at 1600 m−2 scalable foods provided the best survival and growth. Juvenile red king (Table 2, Fig. 2B, C). However, crabs were heavier (95.9±13.5 mg, crab are opportunistic benthic scavengers and have well developed p=0.003) and larger (4.6±0.29 mm) when reared in the absence of feeding appendages adapted for processing both soft and hard food Color

Experiment - add nutritional supplements Astaxanthin & Calcium

14 Color: Hue Hue Index

Daly et al. in review 15 Survival Survival

Daly et al. in review 16 Hatchery Culture: Juvenile Nursery Issues: Cannibalism Size grading -- diet & density

17 Survival Survival

Size Grading Daly et al. in review 18 Survival Survival

Size Grading Daly et al. in review 19 Hatchery Culture: Juvenile Nursery

Increasing survival:

• Complex substrates: reduces antagonistic interactions

20 Hatchery Culture: Juvenile Nursery

Increasing survival:

• Complex substrates: reduces antagonistic interactions

• Size grading: reduces cannibalism on smaller crabs

21 Hatchery Culture: Juvenile Nursery

Increasing survival:

• Complex substrates: reduces antagonistic interactions

• Size grading: reduces cannibalism on smaller crabs