Thomas C. Shirley

Seasonal Migration and Distribution of Female Red King Crabs in a Southeast Alaskan Estuary

ABSTRACT Seasonal movements and distribution of primiparous and multiparous red king crabs (Paralithodes camtschaticus) were monitored with ultrasonic biotelemetry approximately weekly for 1 year in Auke Bay, Alaska. Migration was associated with life-history events and may have occurred in response to spatial and temporal variations in environmental conditions and resources. All crabs displayed distinct shifts in depth and habitat use and followed a general pattern of seasonal movement as follows: (1) gradual movement to deep water in spring after mating and egg extrusion, and residence there through early November; (2) abrupt, synchronous movement into shallow-water areas in November, and residence there through late February or early March; and (3) gradual, synchronous movement to intermediate depths followed by movement into shallow water to molt and mate between late March and late May. The behavior of primiparous crabs was more variable than that of multiparous crabs. The differences in behavior may result from ontogenetic shifts in movements, and habitat selection. The annual range of primiparous crabs (x = 11.9 km2) exceeded that of multiparous crabs x( = 3.6 km2). Mean depth was directly correlated with photoperiod, and the sudden, synchronous movement of crabs between habitats coincided with thermohaline mixing. Females displayed a highly aggregated distribution, especially during winter in shallow water, where podding behavior of adult crabs was documented for the first time.

Larval development of the rhizocephalan cirripede Briarosaccus tenellus (Maxillopoda: Thecostraca) reared in the laboratory: A scanning electron microscopy study

SEM investigations of laboratory-reared larvae of Briarosaccus tenellus Boschma, 1970, revealed five naupliar instars, one more than previously described for the Rhizocephala. The external features of these and the cypris larva are described in detail. The youngest instar (NO) is characterised by a better developed furca than in subsequent stages and one additional antennulary seta. Differences in outline, shape of antennulae, and hind-body denticulation, offer the potential of individual discrimination. All the nauplii possess a transparent, hollow cuticular ring around their body. This ‘flotation collar’ represents the bulged margin of the larval head shield and is attached to the body along a delicate ridge. Three pairs of tiny pores in contact with the ridge possibly regulate inflation of the ring, but details of this mechanisms remain unknown. Due to total lecithotrophy, the nauplii of B. tenellus have limbs setation reduced to that needed for swimming only, and other feeding structures such as the labrum are also highly reduced. In the antennulae, the morphological changes in form and setation were followed from nauplius to cypris and shown to largely resemble events in ontogeny of the thoracican barnacle Semibalanus balanoides. On this basis we establish a homology scheme between antennulary setae in these two species. In both B. tenellus and S. balanoides, a naupliar seta, apically on the fourth antennulary segment develops into a conspicuous aesthetasc while one (B. tenellus) or two (S. balanoides) subapical and postaxially sited setae on the same segment develops into into four short setae in the cypris. Our study reveals that the terminology used in describing cirripede nauplius and cypris larvae is often misleading or even erroneous and improvements are suggested. Notably replacing ‘cypris carapace’ with the ontogenetically and phylogenetically more informative term ‘head shield’.

Lecithotrophic Development of the Golden King Crab Lithodes Aequispinus (Anomura: Lithodidae)

ABSTRACT Larvae of the golden king crab Lithodes aequispinus were reared in individual chambers in the laboratory from hatching to the first crab stage (C1). The experiment included 2 treatments: 1 group was fed live nauplii of Artemia daily, while the other group was unfed. A total of 4 molts were observed for all larvae from hatching to Cl. One larval stage, either zoea III or zoea IV, was skipped by all larvae. No significant difference existed for the duration of development of each stage between fed and unfed treatments. The mean durations were ZI (ZI = zoeal stage I, ZII = zoeal stage II, etc.) = 6.6 days (±0.71 SD), ZIIa (molted to ZIII) = 7.0 d (±0.65 SD), ZIIb (molted to ZIV) = 8.8 d (±0.95 SD), ZIII (skipped ZIV) = 12.0 d (±1.33 SD), ZIV (skipped ZIII) = 9.3 d (± 1.63 SD), and glaucothoe = 41.3 d (±2.65 SD). The total larval duration was approximately 67 d. The survival rate of the fed group was significantly lower than that of the unfed group. Seventeen percent of unfed larvae developed to Cl, but only 0.7% of fed larvae did so. The longest duration of survival from hatching was 191 d for an unfed crab. The dry weights of unfed larvae decreased 10% from hatching to Cl. Our results indicate that the larval development of the golden king crab is fully lecithotrophic, i.e., larvae can successfully develop to juvenile crabs without eating.

Survival, Feeding, and Growth of Juvenile Dungeness Crabs From Southeastern Alaska Reared at Different Temperatures

ABSTRACT Survival, feeding rates, and growth of individual juvenile Dungeness crabs (Cancer magister) were measured over 150 days at 0, 5, 10, 15, and 20°C in a laboratory study. Survival was highest at 0°C (79%) and lowest at 20°C (30%), but the number of surviving crabs declined at all temperatures over time. A high number (75%) of crabs survived at 10 and 15°C, temperatures associated with the greatest increases in size. Feeding rates increased with temperature up to 15°C. Crabs at 0°C did not eat and crabs at 5°C had a low but fairly constant feeding rate. Feeding rates at 10, 15, and 20°C increased significantly early on and then decreased to beginning rates; increases in feeding rates occurred after a large percentage of the crabs molted. Growth, measured by the increase in carapace width and wet weight over time, increased with temperature up to 15°C and then declined. Maximum growth occurred at 15°C. However, no significant differences in carapace width or wet weights existed among crabs at 10, 15, and 20°C by the end of the study. Crabs at 0°C did not molt or increase in weight; crabs at 5°C had very long intermolt periods and increased in weight by only 55%. Temperature effects on the size of molt increments were minimal; at 5, 10, and 15°C there were no significant differences in the size of molt increments. At 20°C the molt increment decreased with crab size. The intermolt period was the growth component most affected by temperature. The warmer the water temperature, up to 15°C, the shorter the intermolt period. Our results are consistent with the belief that Dungeness crabs have longer intermolt periods progressively northward along the west coast of North America.

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.

Behavior of red king crab larvae: phototaxis, geotaxis and rheotaxis.

Zoeae of Paralithodes camtschatica were positively phototactic to white light intensities above 1 x 10(13) q cm-2 s-1. Negative phototaxis occurred at low (1 x 10(12) q cm-2 s-1), but not high intensities (2.2 x 10(16) q cm-2 s-1). Phototactic response was directly related to light intensity. Zoeae also responded to red, green and blue light. Zoeae were negatively geotactic, but geotaxis was dominated by phototaxis. Horizontal swimming speed of stage 1 zoeae < 4 d old was 2.4 +/- 0.1 (SE) cm s-1 and decreased to 1.7 +/- 0.1 cm s-1 in older zoeae (P < 0.01). Horizontal swimming speed of stage 2 zoeae was not significantly different from > or = 4 d old stage 1 zoeae. Vertical swimming speed, 1.6 +/- 0.1 cm s-1, and sinking rate, 0.7 +/- 0.1 cm s-1, did not change with ontogeny. King crab zoeae were positively rheotactic and maintained position in horizontal currents less than 1.4 cm s-1. Starvation reduced swimming and sinking rates and phototactic response.

Behavioural responses of red king crab to crab pots

Abstract High bycatch of female and sublegal sized male king crabs in the fishery is of concern to fishermen and management agencies; the efficiency of gear currently used in the fishery needs to be improved. This study examined behavioural responses of red king crabs to pots under laboratory conditions with time-lapse video. Crabs approached the pot from downstream, 82% of searches were confined to within 135 ° of the downstream direction, and 78.3% of crabs searched less than 90 ° before leaving or entering. The probability of entry success increased with the number of approaches. Crabs which failed to enter made an average of 2.6 approaches compared with 3.9 approaches for crabs which entered pots. The entry success rate was 8.1%. No significant differences in approach, search, and entry were found between ovigerous females, juvenile females, legal-sized males, and sublegal-sized males. Legal males (≥ 178 mm carapace width) had a significantly lower escape attempt rate and escape rate than sublegal males and females. Crabs depend on chemical cues during foraging, approaching, and searching. The current king crab pot is inefficient because crabs have difficulties in accessing the entrances and non-legal crabs have difficulties in escaping.

A new meiobenthic priapulid (Priapulida, Tubiluchidae) from a Mediterranean submarine cave

Abstract A new priapulid species belonging to genus Tubiluchus is described on the basis of specimens collected in November, 2000 and June, 2001 in a submarine cave along the Ionian coast of Apulia, Southern Italy. The new species closely resembles T. corallicola that inhabits the tropical‐subtropical areas of the Western Atlantic Ocean but can be distinguished by the smaller size of the adults, and the smaller size and the shape of the pharyngeal teeth of the larval stages. A careful microscopical survey of the sensorial elements led to the discovery of a central bristle in the flosculi and a small hole at the tip of the associated setae, allowing speculation about a tactile sensorial function for the former and a chemoreceptive function for the latter. While T. troglodytes n. sp. represents the first fully described species of this genus from the Mediterranean Sea, the population densities recorded, particularly those found in June, 2001 (83.8 ± 40.1 SD ind./10 cm2) rank among the highest value reported for priapulids from any location in the world. On both sampling dates the sex ratio (female/total adults) in the T. troglodytes n. sp. population averaged about 0.6. Presence of larval stages of different ages during both sampling periods could imply that Tubiluchus spp reproduce the year around.

Diel vertical migration and seasonal timing of the larvae of three sympatric cancrid crabs,Cancer spp., in Southeastern Alaska

Diel vertical migration (DVM) and seasonal timing of three sympatricCancer spp. larvae were investigated in southeastern Alaska. Diel sampling was conducted at a station in Icy Strait at 0400, 0700, 1000, 1300 h in the first day, and 1300, 1600, 1900, and 2200 h in the second day from June to September 2001. Larvae were collected with Bongo nets (333 and 505 μm mesh) towed vertically from 20 m depth to the surface. During flood tides surface temperature increased slightly and salinity decreased; the reverse occurred during ebb tides. Zooplankton biomasses were higher in the early morning and evening than during the midday. A total of 4,482 larvae were examined for the study.Cancer oregonensis larvae were most abundant (4,238), followed byC. magister (205) andC. productus (39). Larval density peaked in June while no larvae were found in September.C. magister larvae had a crepuscular migration; larval abundance peaked in early morning and evening.C. oregonensis larvae comprised 94.6% of allCancer spp. larvae collected and had a strong DVM in June. Earlier zoeal stages ofC. oregonensis were relatively more abundant during midday, while later stages were more abundant at night. In July, later larval stages ofC. oregonensis were distributed at the surface all day with a peak at 2200 h. Larvae ofC. productus first occurred in July and peaked in August.C. productus had DVM but many were at the surface diurnally.C. magister andC. oregonensis larvae co-occurred seasonally as they do in the lower latitudes, e.g., Washington and British Columbia; however,C. productus appeared approximately 2 mo later thanC. magister andC. oregonensis in southeastern Alaska.

Halicryptus higginsi n.sp. (Priapulida): A Giant New Species from Barrow, Alaska

A new species of Priapulida was discovered from the Beaufort Sea near Barrow, Alaska. Following an unusually strong autumnal storm, 30 adult specimens of Halicryptus higginsi n.sp. were collected, many alive, from intertidal beaches Additional specimens were found in museum collections misidentified as Halicryptus spinulosus von Siebold 1849. The new species represents the 11th priapulid species described since 1968 and increases the number of described extant species of Priapulida to 18. While all other recently described priapulids have been meiofaunal, Halicryptus higginsi n.sp. is macrofaunal and the largest extant priapulid species, with one specimen being 39 cm long in a contracted condition. Additional key words: arctic, benthos In recent years the concept of the marine phylum Priapulida has changed radically, from that of a macrobenthic, cold-water taxon, to one that is more speciose in the tropical meiofauna. Before 1968, only 7 extant species were known and additional species had been described from the fossil record; all extant species were macrobenthic and found only in cold-water habitats (Higgins et al. 1993). In 1968 the first meiobenthic priapulid, Tubiluchus corallicola VAN DER LAND 1968, was described from a tropical, shallowwater habitat (van der Land 1968). Since 1968 an additional 9 priapulid species, all meiobenthic and mostly inhabitants of tropical, shallow-water sediments, have been described. Tubiluchus arcticus ADRIANOV, MALAKOV, CHESUNOV, & TSETLIN 1989 is the only cold-water species that has been described in recent years, and it is a meiofaunal priapulid that inhabits shallow-water sediments in the arctic (Adrianov et al. 1989). During a survey of museum specimens of priapulids, one of us (VS) discovered that specimens in the United States National Museum of Natural History, Smithsonian Institution, misidentified as Halicryptus spinulosus von Siebold from Barrow, Alaska, had been used for scanning electron microscopy (Merriman 1981) and instead represented a new and undescribed congener. Subsequent to the museum discovery we found larvae and juveniles of the undescribed species a Author for correspondence. E-mail: fftcs@uaf.edu in the shallow subtidal during two expeditions to Barrow, Alaska in 1991 and 1992, but did not find adults of the new species. Following an unusually strong autumnal storm in 1993, 30 adult specimens of Halicryptus higginsi n.sp. were collected, many alive, from intertidal beaches near Barrow. In this paper we describe the new species and compare it with H. spinulosus. The larvae will be described in a separate pub-