Ginny L. Eckert

Changes in Embryonic Development and Hatching in Chionoecetes opilio (Snow Crab) With Variation in Incubation Temperature

Water temperature affects the distribution, movement, and reproductive potential of female snow crab, Chionoecetes opilio. Ovigerous females of C. opilio from the eastern Bering Sea were held at five temperatures (−1, 0, 1, 3, and 6 °C) in the laboratory while their embryos developed from gastrula to hatching. The duration of incubation increased by 105 d (30%) with decreasing temperature; however, a switch to a 2-year duration of embryo incubation was not observed. For females held at 6, 3, and 1 °C, their embryos underwent a short period of diapause late in development; no diapause was observed for embryos of females held at 0 or −1 °C. Successful extrusion of a subsequent clutch and hatch timing comparable with that observed in the eastern Bering Sea indicated that temperatures of 0 to 3 °C may be optimal for multiparous female reproduction. We demonstrated that a switch from 1-year to 2-year reproduction cannot be triggered by changing the thermal regime after several months of embryonic development. The timing of female movement from colder to warmer waters may be important for maintaining population reproductive potential during the recent phase of warming and contraction of cold-water biomes in the Bering Sea.

Red King Crab, Paralithodes camtschaticus, Size-Fecundity Relationship, and Interannual and Seasonal Variability in Fecundity

ABSTRACT Stock assessment of Alaska red king crab, Paralithodes camtschaticus, can be improved by incorporating embryo production, which requires an understanding of the size-fecundity relationship and an understanding of interannual and seasonal variability in fecundity. We collected red king crab egg clutches from Bristol Bay, AK, during summer 2007 to 2010 and autumn 2007 to 2009 and estimated individual fecundity using dry weight methods. Fecundity increased with female size up to 138 mm carapace length (CL), at which point the slope decreased by 40%, suggesting senescence. Fecundity varied significantly but slightly (maximum, 5%) among years. Fecundity was consistently lower in autumn than spring, suggesting brood loss, with a 6% decrease between seasons in females smaller than 138 mm CL and a 10% decrease in larger females. When incorporating embryo production in stock assessments, differences in the size-fecundity relationship should be accounted for and rates of brood loss can be used to predict larval output more effectively if fecundity cannot be measured shortly before hatching. To include potential environmental effects on the relationship, time series of fecundity and female size should be extended over a wider range of future temperature conditions.

Total Lipids, Lipid Classes, and Fatty Acids of Newly Settled Red King Crab (Paralithodes camtschaticus): Comparison of hatchery-cultured and wild crabs

ABSTRACT Little is known about the nutrition or lipid metabolism of cold-water crabs, particularly in the North Pacific. We undertook a 2-part study to understand more completely the energetics and nutritional requirements of juvenile red king crab (RKC; Paralithodes camtschaticus). First, we investigated changes in proximate composition, total lipids (TLs), lipid classes, and fatty acids (FAs) throughout a molt cycle (C4–C5). Trends in lipid parameters were described by a 3-part piecewise linear regression with 3 distinct stages: (1) a postmolt phase (∼0–7 days), (2) an intramolt stage (∼7–24 days), and (3) a premolt stage (∼24–33 days). Significant intramolt differences in TLs indicated that caution should be taken when comparing crabs of unknown molt stage in future aquaculture and ecological experiments. However, little variability was found in the proportional FA composition of crabs, indicating that the intramolt stage has little effect on the interpretation of FA biomarkers. During a second investigation, we examined differences in lipid classes and FAs from cultured and wild RKC. We found significantly higher proportions of the essential fatty acids (EFAs) 20:5n-3 (EPA) and 20:4n-6 (AA) in wild crabs compared with cultured animals at the same stage. Furthermore, higher proportions of bacterial markers and lower proportions of Zooplankton FA markers were found in wild than in hatchery-reared crabs. Here, we provide the first baseline data for future dietary studies on juvenile cold-water crabs. We suggest that an initial EFA ratio for DHA:EPA:AA of 5:8:1 could be used as a starting point for controlled dietary studies on the effect of EFAs on juvenile growth, molt success, and survival.

Tag Retention and Effects of Tagging on Movement of the Giant Red Sea Cucumber Parastichopus californicus

Abstract We examined tag retention and the effects of tagging on short-term movements of the giant red sea cucumber Parastichopus californicus. Retention rates were monitored for six different tag types (Floy banner FTSL-73, cinch FT-4C, fingerling FTF-69, garment, single T-bar FD-94, and the coded wire tag), which were applied to 30 individuals under laboratory conditions. The single T-bar and coded wire tag had the highest retention rates: 70% and 60% after 16 weeks, and 40% and 37% after 32 weeks. To assess the effects of tagging and handling on movement, a field study was conducted in Amalga Harbor, Alaska, in which giant red sea cucumbers were tagged with T-bar tags and monitored for 24 h. Tagged and handled animals moved significantly farther than control animals. The median (linear) distance moved by control animals over 24 h was 1.8 m (range, 0.2–4.2 m), whereas the median distance for tagged animals was 4.2 m (range, 0.4–22.7 m). Short-term behavior was affected by both tagging and handling; ther...

Comparison of first year growth among field, hatchery- and laboratory-raised juvenile red king crab, Paralithodes camtschaticus (Tilesius, 1815), in Alaska

In an effort to better understand juvenile growth in the first year and to determine potential effects of hatchery larval rearing, we compared growth of juvenile red king crab, Paralithodes camtschaticus (Tilesius, 1815), in the field and under laboratory-rearing conditions. Glaucothoe were obtained from the Alutiiq Pride Shellfish Hatchery and field; once molted to first stage juveniles, both sets were raised individually in the laboratory under ambient conditions (hereafter called hatchery/laboratory-reared and wild/laboratory-reared, respectively) and measured at each molt. Field-surveyed juveniles were observed and measured monthly in the intertidal in Juneau, AK, USA. Size, molt interval, cumulative molt interval, and molt increment did not differ significantly between hatchery/laboratory-reared and wild/laboratory-reared crab or between male and female crab over one year. Crab reached an average size ± SD of 13.6 ± 2.1 mm CL after 10-11 molts/year with 24% average molt increment at ambient temperatures. Carapace lengths of hatchery/laboratory-reared, wild/laboratory-reared, and field-surveyed juveniles were not significantly different in five of eight months from January through August, with small differences in January, February, and May, likely resulting from differences in hatch timing. Spine lengths differed from January through March but not from April through August. Spine lengths of hatchery/laboratory-reared crab were significantly larger than field-surveyed crab from January through March. Wild/laboratory-reared crab had significantly longer spine lengths than field-surveyed crab in February and March. In conclusion, growth did not differ significantly among juveniles reared in the laboratory and from the field.

Does maternal size affect red king crab, Paralithodes camtschaticus, embryo and larval quality?

Stock assessment of Alaskan red king crab, Paralithodes camtschaticus (Tilesius, 1815), can be improved by incorporating reproductive output, which requires an understanding of maternal size effects on embryo and larval quality. In June 2009 and 2010, we collected clutches of recently extruded red king crab embryos in Bristol Bay, Alaska, to assess embryo quality based on dry weight, carbon and nitrogen content. To assess larval quality, we collected ovigerous females from Bristol Bay in 2007 and reared them in the laboratory until larval hatching in 2008. Larval quality based on dry weight, carbon and nitrogen content, and times to 50% mortality under starvation conditions were assessed. All samples were collected in years that were colder than the 15-year average in the eastern Bering Sea. Among the measures of embryo quality, only nitrogen content was significantly different, increasing with maternal size. Carbon and nitrogen content were significantly higher for embryos in 2009 than in 2010, suggesting inter-annual differences in maternal investment. No effect of maternal size with larval quality was found. Our results indicate that maternal size does not have a biologically significant effect on embryo and larval quality in colder-than-average years, and therefore maternal size effects on embryo and larval quality does not need to be explicitly incorporated into reproductive output estimates in stock assessments under these conditions. We are, however, cautious to extrapolate our results to years with different environmental conditions. Further study is needed to fully resolve the possible interaction of environment with maternal size effects on embryo and larval quality for red king crab.

Enhancing Shellfish Safety in Alaska through Monitoring of Harmful Algae and Their Toxins

ABSTRACT Harmful algal blooms cause serious problems to public health and the economic viability of shellfish industries in Alaska. The most common phycotoxins in this region are saxitoxin and its congeners, collectively referred to as paralytic shellfish toxins, the causative agents of paralytic shellfish poisoning (PSP) in humans. The illness of 26 and death of 2 people in southeast Alaska as a result of PSP in 2010 through 2012 illustrates the need for change in the way paralytic shellfish toxins are monitored and managed in Alaska. The implementation of a scientific monitoring partnership, the Alaska Harmful Algal Bloom monitoring network, designed to provide an early warning of harmful algal blooms—in particular, those that cause PSP—is described. The program includes a tiered sampling approach, and weekly microscopic observation of seawater samples for the presence of the causative toxic dinoflagellate Alexandrium, followed by rapid toxin testing using a high-throughput antibody-based test as a complement to the standard regulatory testing performed by managers at the Alaska Department of Environmental Conservation. Partners in the Alaska Harmful Algal Bloom monitoring network began monitoring in 2008 and thus were able to provide an early warning of a widespread PSP event near Ketchikan in 2011, and the environmental conditions preceding a shellfish closure resulting from paralytic shellfish toxins near Mosman Island in southeast Alaska in 2012. A comprehensive and integrative communication network between Alaska Harmful Algal Bloom monitoring network personnel and state managers, health professionals, shellfish growers, and the general public is proposed to protect human health and promote safe shellfish harvest in Alaska.

qPCR assays for Alexandrium fundyense and A. ostenfeldii (Dinophyceae) identified from Alaskan waters and a review of species-specific Alexandrium molecular assays

Abstract: Paralytic shellfish poisoning (PSP) poses a serious health threat in Alaska and prevents effective utilization of shellfish resources by subsistence and recreational harvesters. Substantial economic losses also affect shellfish growers during PSP events. The toxins responsible for PSP are produced by dinoflagellates in the genus Alexandrium. Despite the persistent threat posed by PSP and the long history of shellfish toxicity research, there is still confusion concerning the Alexandrium species that cause PSP in Alaska. The primary objective of this study was to identify the toxic Alexandrium species present in Alaska and to develop polymerase chain reaction (PCR) assays for use in screening phytoplankton and sediment samples. Before developing the PCR assays for this study, we evaluated published assays and many were not adequate because of primer dimer formation or because of cross-reactivity. Rather than continue to grapple with the uncertainty and inadequacy of published assays, we developed new assays for the Alexandrium species most likely to be present in Alaska. Only Alexandrium fundyense Group I and A. ostenfeldii were identified from four sampling regions from southeast Alaska to Kodiak Island, indicating that these two species are widely distributed. PCR assays for these two species were converted to quantitative (q)PCR format for use in monitoring programs. During the course of this study, we realized that a systematic evaluation of all published (~150) Alexandrium species-specific assays would be of benefit. Toward this objective, we collated published Alexandrium PCR, qPCR, and in situ hybridization assay primers and probes that targeted the small-subunit (SSU), internal transcribed spacer (ITS/5.8S), or D1–D3 large-subunit (LSU) (SSU/ITS/LSU) ribosomal DNA genes. Each individual primer or probe was screened against the GenBank database and Alexandrium gene sequence alignments constructed as part of this study. These data were used to identify a suite of species-specific Alexandrium assays that can be recommended for evaluation by the global harmful algal bloom community.

Influence of temperature and congener presence on habitat preference and fish predation in blue (Paralithodes platypus Brandt, 1850) and red (P. camtschaticus Tilesius, 1815) king crabs (Anomura: Lithodidae)

Rebuilding fisheries is a difficult process and many stocks that are declared overfished fail to recover even in the absence of fishing pressure. The Pribilof Islands stock of the blue king crab ( Paralithodes platypus Brandt, 1850) in Alaska, USA is one of these recovery failures. To explore how environmental and ecological factors might interact to suppress this stock, we conducted a suite of laboratory experiments to assess the effects of temperature changes and the presence of red king crab ( Paralithodes camtschaticus Tilesius, 1815) on blue king crab habitat preference and fish predation survival. Age-0 blue king crabs exhibited plasticity in habitat preference mediated by changes in water temperature, as well as the presence and density of juvenile red king crabs. While blue king crabs are often associated with shell-hash habitat, increases in water temperature, as well as the presence of red king crab at high densities, caused blue king crab juveniles to shift into habitats with an algal mimic present, a habitat type shown to reduce the predation efficacy of red king crabs. In contrast, red king crabs exhibited fewer changes in habitat preference with changes in water temperature and the presence of a congener. Blue king crabs are therefore behaviorally plastic, switching from strategies of predator avoidance when predator encounter rates are likely low, to predator deterrence strategies when encounter rates are higher. Fish predation trials further support the idea that blue king crabs are more focused on predator avoidance than are red king crabs. In fish predation trials run separately for the two crab species, blue king crabs had higher survival (60%) than red king crabs (33%) when exposed to fish predators. Our results indicate that age-0 blue king crabs can be less vulnerable to fish predation than red king crabs, but future research should assess how fish predation rates change when presented with higher densities of red and blue king crab in mixed assemblages as the observed habitat shifts could affect predation survival.

Development of a Real-Time Pcr Assay for Detection of Planktonic Red King Crab (Paralithodes camtschaticus (Tilesius 1815)) Larvae

ABSTRACT The Alaskan red king crab (Paralithodes camtschaticus) fishery was once one of the most economically important single-species fisheries in the world, but is currently depressed. This fishery would benefit from improved stock assessment capabilities. Larval crab distribution is patchy temporally and spatially, requiring extensive sampling efforts to locate and track larval dispersal. Large-scale plankton surveys are generally cost prohibitive because of the effort required for collection and the time and taxonomic expertise required to sort samples to identify plankton individually via light microscopy. Here, we report the development of primers and a dual-labeled probe for use in a DNA-based real-time polymerase chain reaction assay targeting the red king crab, mitochondrial gene cytochrome oxidase I for the detection of red king crab larvae DNA in plankton samples. The assay allows identification of plankton samples containing crab larvae DNA and provides an estimate of DNA copy number present in a sample without sorting the plankton sample visually. The assay was tested on DNA extracted from whole red king crab larvae and plankton samples seeded with whole larvae, and it detected DNA copies equivalent to 1/10,000th of a larva and 1 crab larva/5mL sieved plankton, respectively. The real-time polymerase chain reaction assay can be used to screen plankton samples for larvae in a fraction of the time required for traditional microscopial methods, which offers advantages for stock assessment methodologies for red king crab as well as a rapid and reliable method to assess abundance of red king crab larvae as needed to improve the understanding of life history and population processes, including larval population dynamics.