AFSC/RACE/SAP/Swiney: Red king crab fecundity and embryo and larval quality

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Bristol Bay, Alaska.

Note: Dataset migrated by Dan Woodrich (AFSC data management coordinator) on 12/16/2021. Contact: Daniel.woodrich@noaa.gov

Donaldson, W. E. and Byersdorfer, S. C. 2005. Biological field techniques for lithodid crabs. Alaska Sea Grant College Program, University of Alaska. 82 pp.

Cited in the methods section

Otto,R. S, R. A. MacIntosh, and P. A. Cummiskey. 1990. ¿Fecundity and other reproductive parameters of female red king crab (Paralithodes camtschatica) in Bristol Bay and Norton Sound, Alaska. International Symposium on King and Tanner crabs, Alaska Sea Grant AK0SG-90-04. 65-90 pp.

Manuscript cited in the methods section

Swiney, K. M., J. B. Webb, G. H. Bishop, and G. L. Eckert. 2010. ¿Temporal and spatial variability of Alaska red king crab fecundity, and accuracy of clutch fullness indices in estimating fecundity. Biology and Management of Exploited Crab Populations under Climate Change. Alaska Sea Grant AK-SG-10-01. 265-282 pp.

Manuscript produced from this data

Swiney, K. M., Long, W. C., Eckert, G. L., and Kruse, G. H. 2012. Red king crab, Paralithodes camtschaticus, size-fecundity relationship, and interannual and seasonal variability in fecundity. Journal of Shellfish Research 31(4): 925-933.

Manuscript produced from this data

Swiney, K. M., Eckert, G. L., and Kruse, G. H.Does maternal size affect red king crab, Paralithodes camtschaticus, embryo and larval quality? Journal of Crustacean Biology 33(4): 470-480.

Manuscript produced from this data

Swiney, K. M. and Long, W. C. 2015. Primiparious red king crab Paralithodes camtschaticus are less fecund than multiparous crab. Journal of Shellfish Research 34(2): 493-498.

Manuscript produced from this data

To compare inter-annual and seasonal variability in red king crab fecundity, egg clutches of ovigerous females were collected from Bristol Bay, Alaska, in summer and autumn. Summer samples were collected during June to July 2007, 2008, 2009, 2010 and 2012 during bottom trawl surveys conducted by NMFS and autumn samples were collected during October to November 2007, 2008, and 2009 by observers from sampled bycatch aboard pot (trap) vessels during the commercial fishery. In summer 2007, ovigerous females were sampled from 10-mm size bins between 90 and 140 mm CL and samples were preserved at sea in 10% buffered formalin. For the rest of the collections, ovigerous females were sampled from 10-mm size bins between 80 and 150+ mm CL and samples were frozen at sea. For all of the collections, ovigerous females were haphazardly collected until 20 clutches per size bin were attained regardless of clutch size. In summer samples, only females that recently extruded eggs and were brooding uneyed embryos were collected. Samples were collected by either carefully removing the abdominal flap with attached embryos and placing the abdomen in a cloth bag or by placing the entire female with the legs removed in a plastic bag. In either case, the bags were closed in a way to prevent embryo loss. Upon collection, female carapace length were measured to the nearest 1.0 mm, and clutch fullness were recorded using the methods of Donaldson and Byersdorfer (2005).

Fecundity was determined using dry weight methods modified from Otto et al. (1990). Embryos were carefully stripped off the pleopods and then two random samples of 250 embryos were counted. The subsamples and remaining embryos were dried at 60°C until a constant weight was achieved. Fecundity was estimated by dividing the total dry weight of embryos by the average of the two estimates of individual embryo dry weight obtained from the subsamples.

To determine the percentage of embryos that was viable, clutches were examined for the presence of non-viable embryos in summer 2008 and 2009 and autumn 2007, 2008, and 2009. Non-viable eggs were identified by abnormal shape, color, asymmetrical cell cleavage in summer samples and absence of an eyed-embryo in autumn samples. For recently extruded eggs, freezing and formalin preservation prevented determination of embryo viability. So, for summer collections a random sample of fresh embryos were removed from a subset of the females collected for fecundity estimation and placed in labeled vials of seawater. Vials were kept chilled while at sea and examined under a dissecting microscope immediately upon arrival at the laboratory. In the autumn, all clutches with eyed embryos were examined for the percentage of viable embryos which was determined from the two subsamples of 250 embryos counted for fecundity estimation. If embryo eyes could not be seen macroscopically, then embryos were examined microscopically to determine viability.

To examine maternal size effects and inter-annual variability in embryo quality, embryo clutches of ovigerous females were collected from Bristol Bay, Alaska, in June 2009 and 2010 during the National Marine Fisheries Service (NMFS) bottom trawl survey in the eastern Bering Sea. A subset of samples collected for the fecundity study were examined for embryo quality. Ten samples from 3 size bins (86-95 mm, 111-120 mm, and 136-145 mm CL) for a total of 30 were randomly chosen from the fecundity collections. Only females that recently extruded eggs and were brooding uneyed embryos were chosen. Samples were collected at sea by carefully removing the abdominal flap with embryos attached and placing the abdomen into a sealed cloth bag to ensure that no embryos were lost, and then frozen.

We assessed embryo quality by measuring embryo dry weights, carbon content, and nitrogen content. To estimate embryo dry weight and fecundity, embryos were carefully stripped off of the pleopods and then two random samples of 250 embryos each were counted. The subsamples and remaining clutch were dried at 60°C until a constant weight was achieved. Individual embryo weights were calculated for each subsample and averaged to obtain the mean embryo dry weight for an individual crab. Fecundity was estimated by dividing the total dry weight of all embryos by the mean embryo dry weight. From each female, a few hundred embryos were dried, finely ground to a powder, and approximately 0.2 g of sample were sent to an analytical laboratory for carbon and nitrogen content analysis using the Dumas combustion method with an automated organic elemental analyzer (Gnaiger and Bitterlich, 1984).

To assess maternal size effects on larval quality, live ovigerous red king crab were collected from Bristol Bay, Alaska, November 2007 by onboard observers during the commercial fishery. Crab were shipped to the NMFS Kodiak Seawater Laboratory where they were reared in a tank with flow-through, sand-filtered seawater. The seawater was chilled to approximate monthly average Bristol Bay bottom temperatures ranging from 1.7 to 4.4° C (mean = 2.7° C, SD = 0.8). Crab were fed ad libitum a diet of fish and squid biweekly. At the beginning of April 2008 each crab was transferred to an individual tub with flow-through seawater and netted outflows to monitor hatching. When an individual crab hatched approximately 500 larvae, the female was moved to a non-flow-through tub overnight to collect viable larvae for experiments; larvae were damaged in nets of the flow-through tubs and therefore not viable for experiments. The tub was placed in a bigger tank with flowing water that served as a water bath to maintain the proper water temperature in the tub; additionally an airstone was placed in the tub to oxygenate the water. In the morning active, phototactic larvae were collected for the experiments. Larvae from 35 females of sizes 93-134 mm CL were used in starvation survival experiments to measure larval fitness. Twenty-five larvae from each female were collected and used in each of 3 replicates, for a total of 75 larvae per each of the 35 females. For each replicate, 25 larvae were placed in a 10.16 cm diameter PVC tube with 650 micron mesh glued to the bottom. The PVC tubes were placed in 2 L beakers filled with UV sterilized filtered seawater. The experiments were conducted in a cold room at 8° C with a cycle of 12 hours light (1.4 lux) and 12 hours dark. Water was changed biweekly and larvae were not fed. Beakers were checked daily for molts and mortalities. A larva was considered dead when it had no color and did not move when observed in a pipette for 10 seconds. Lethal time to 50% mortality (LT50) was calculated as the average number of days when at least 50% mortality was observed. Larvae from each of the female crab used in the starvation experiment were collected upon hatching and dried at 60°C until a constant weight was achieved for measurements of dry weight and carbon and nitrogen analysis. Twenty dried larvae per female were weighed individually and averaged to estimate mean larval weight at the start of the survival experiments. From each female, a few hundred larvae were dried, finely ground to a powder, and approximately 0.2 g of sample were sent to an analytical laboratory for carbon and nitrogen content analysis, as described above for embryos.