A. J. Paul

Fall and spring somatic energy content for Alaskan Pacific herring (Clupea pallasi Valenciennes 1847) relative to age, size and sex

Abstract During the fall of 1995 and spring of 1996, the whole body energy content (WBEC) of Pacific herring ( Clupea pallasi Valenciennes 1847) from Prince William Sound, Alaska, was examined. Somatic energy (kJ·g −1 wet wt.) exhibited a wide range of values relative to fish length. In the fall young of the year (YOY) recruits had an average of 5.7 kJ·g −1 wet wt. for whole body samples vs. 8.0 for age 1 and 9.4–10.2 kJ·g −1 for fish of ages 2 to 7. The following spring the 1995 year class which had just survived their first winter averaged 4.4 kJ·g −1 wet wt. for somatic samples, and age 1 fish had similar values, while herring ages 2 to 7 had WBEC>5 kJ·g −1 . The difference in somatic energy content between adult male and female fish captured in fall and again in the spring just prior to spawning, was about 4 kJ·g −1 wet wt., or about a 40% change. The difference in mean values for somatic energy content for YOY herring was only about 1.4 kJ·g −1 suggesting either the recruits ate more food during the winter than the adults, had lower energetic needs, or only those with higher than average energy stores survived the winter. The fall measures of WBEC showed the YOY and age 1 fish stored markedly less energy to over-winter than older herring. Thus, energetically the recruiting year class, and those entering their second winter, are the most at risk of over-winter mortality.

Energy sources for first-feeding zoeae of king crab Paralithodes camtschatica (Tilesius) (Decapoda, Lithodidae)

The occurrence of first zoeae of king crab Paralithodes camtschatica (Tilesius) and potential phytoplankton food was monitored during April 1987 in Auke Bay, Alaska. The most abundant phytoplankton were Thalassiosira spp. and Skeletonema costatum (Greville) with fewer Chaetoceros spp. Copepod nauplii were the most abundant Zooplankton. Laboratory experiments were done to see if these potential foods, at concentrations simulating those observed to coexist with the larvae, could provide first-feeding king crab zoeae with a positive energy balance. The percentage of zoeae I molting to stage II when grazing on pure cultures of T. nordenskioldii Cleve (4000 cells · ml−1), C. debilis Cleve (2400 cells · ml−1) and S. costatum ( 16 000 cells · ml−1 ) were 96, 5 and 27 %, respectively. Thalassiosira spp. concentrations in the chlorophyll maximum were up to 10 times higher than necessary for 100% of the larvae to molt successfully to stage II. S. costatum was abundant enough in the chlorophyll maximum layer to provide supplemental energy for the zoeae. Chaetoceros spp. were not abundant enough to allow the zoeae to molt if that genus was the sole source of energy. While the percentage of zoeae molting to stage II showed some relationship to cell concentration or algal taxon, these factors had no effect on development time, even at concentrations less than optimal. The first zoeae were not efficient at capturing copepod nauplii or barnacle nauplii when they existed at abundance levels observed in the bay. The results indicated that some diatom taxa are an important energy source for first-feeding king crab larvae and that hatching concurrently with the spring phytoplankton bloom may be an important factor affecting their survival. Factors which modify phytoplankton species succession and formation of a strong chlorophyll maximum layer during the planktonic phase of larval king crab may also be important in determining survival of first feeding larvae.

Second Clutch Viability of Chionoecetes Bairdi Rathbun (Decapoda: Majidae) Inseminated Only at the Maturity Molt

ABSTRACT The ability of female Chionoecetes bairdi, that copulated only one time following their maturity molt, to fertilize subsequent egg clutches was monitored. One group (N = 10) was held with males and the other (N = 11) without them until the extrusion of their second annual egg clutch. All 10 females with access to males produced second clutches with 95-100% of their eggs dividing. In the group of 11 isolated from males only 9% (N = 1) of the females produced clutches in which eggs initiated division. Females with access to males had more eggs in their clutches than the isolated females. A single insemination at the maturity molt typically did not provide sufficient stored sperm to fertilize subsequent egg clutches in C. bairdi. Apparently multiple inseminations are an important aspect of the reproductive biology of this species.

Comparisons of whole body energy content of captive fasting age zero Alaskan Pacific herring (Clupea pallasi Valenciennes) and cohorts over-wintering in nature

Abstract Changes in whole body energy content (WBEC) of captive age-0 Pacific herring ( Clupea pullasi Valenciennes) forced to fast during winter was measured and compared to cohorts collected in the field. Somatic energy content (kJ·g −1 wet wt) of fasting captives declined at a rate of 23 J·g −1 wet wt per day from 1 December 1995 to 25 January 1996 (56 days) at a mean temperature of 6.6°C. In another observation, fish captured on 1 December 1995 and held without feeding until 1 April 1996 (122 days) had an average WBEC that changed from 5.2 to 3.2 kJ·g −1 wet wt during captivity at about 5.2°C. Fish that died during fasts had WBEC values ranging from 2.8 to 3.6 kJ·g −1 wet wt. During March 1996 the WBEC of field collected age-0 herring averaged 3.8 kJ·g −1 , with ≈40% having WBEC ≤3.6 kJ·g −1 wet wt. Thus, by March the average recruit had used most of its stored energy. These observations confirm that in the northern Gulf of Alaska region age-0 herring rely heavily on stored energy to survive their first winter.

Development of Larvae of the Golden King Crab Lithodes Aequispinus (Anomura: Lithodidae) Reared at Different Temperatures

Unfed lecithotrophic larvae of the golden king crab Lithodes aequispinus were reared at 3, 6, and 9?C in darkness and 33-34 ppt salinity. This study was done to improve our understanding of larval development time and the ability of the larvae to survive under different seasonal thermal conditions. The survival rates and intermolt duration was observed for the first zoeal molt (ZI), second molt (ZII), third molt (ZIII), and glaucothoe (G). The duration from hatching to the start of the first nonlarval stage (crab I) averaged 148, 94, and 75 days at 3, 6, and 9?C, respectively. Development rate for ZI to Crab I versus the rearing temperature was described by the equation: Development period (days) = -35.82 (Rearing Temperature ?C) + 1.96 (0C2) + 238.6; r2 = 0.99. Regardless of stage, every degree increase in temperature reduced the length of the development period by approximately 9%. Survival rates of ZI larvae were typically >97% regardless of temperature. By the completion of the ZII molt 83-87% were still surviving. Survival rates to the end of the ZIII molt at 3? and 6?C were 77% and 75%, but only 65% at 9?C. Within stages there was no significant difference in survival rates for ZI, ZII, or ZIII at the 3 test temperatures. The survival rate through the glaucothoe stage was 47% and 51% for larvae reared at 3? and 6?C, respectively, while only 16% of those at 9?C survived to Crab I. There was no significant difference in the percentage of glaucothoe surviving at 3, 6, and 9?C. The golden king crab Lithodes aequispinus Benedict accounts for about 50% of all king crab landings in western Alaska (Otto, 1990) and because of its value there is interest in developing a sound biological basis for management (Shirley and Zhou, 1997; Adams and Paul, 1999). The larvae are large (ZI = 7 mm) nonfeeding organisms that in captivity exhibit both planktonic and benthic habits (Shirley and Zhou, 1997; Adams and Paul, 1999). Since juveniles are found geographically separated from adults, it has been hypothesized that the larvae are planktonic (Hiramoto, 1985; Sloan, 1985; Blau et al., 1996). Much of their habitat is in remote sites where temperatures of the water column are not monitored. In the bays of the North Pacific, juveniles live at 30 ZI were present. A total of 240 larvae were used in the study, 30 collected from each of the 8 females. The 30 larvae from each female were divided into 3 lots of 10 each. Each lot of 10 larvae was

Respiratory energy requirements of the cod Gadus macrocephalus Tilesius relative to body size, food intake, and temperature

Measurements of oxygen consumption rates were made for both fed and unfed Pacific cod Gadus macrocephalus Tilesius at a variety of temperatures. Rates of oxygen consumption were found to be similar to those reported previously for Atlantic cod. At 6.5 °C, Vo2 was described by the equation ml O2 · ind−1 · h−1 = 0.158 (wet wt g0.078); r2 = 0.97. Increase in environmental temperature between 3.5 and 7°C resulted in a linear increase in rates of oxygen consumption. Between 7 and 12 °C, rates of oxygen consumption were similar. When fish were fed a single meal, oxygen consumption rates increased during the 1st and 2nd days after feeding, by ≈ 34 and 18%, respectively, over unfed rates. When fed daily, rates of oxygen consumption increased to peaks of 41–48% over unfed rates, depending on the temperature.

SIZE OF MATURITY IN MALE GOLDEN KING CRAB, LITHODES AEQUISPINUS (ANOMURA: LITHODIDAE)

Abstract Typically ≥90% of the eggs in clutches fertilized by hardshell Prince William Sound Lithodes aequispinus males ≥107 mm carapace length initiated division. Golden king crab males with only one chela and those with post-molt carapaces ≥11 days old were effective parents. Some test males had exclusive access to three ripe females. Their first and second mates all produced viable clutches with 81–100% of eggs exhibiting development. Not all males induced a third female to ovulate. The percentage of eggs initiating division in the clutches of their third potential female mates ranged from 56 to 100%.

Abundance and Taxa Composition of Copepod Nauplii Over Southeastern Bering Sea Deep Water Spawning Grounds of Walleye Pollock, Theragra Chalcogramma

This project examined the abundance, taxa, stage and size of copepod nauplii available as prey for walleye pollock larvae in its deep water spawning grounds of the southeastern Bering Sea. Nauplii of the genera Oithona, Eucalanus, and Metridia were the most commonly encounted types while Pseudocalanus and Microcalanus were rare. There was marked interannual variation in the taxa and abundance of copepod nauplii coexisting with the pollock larvae. Stages I-IV of Oithona were present at 0 to 8 l-1 at different depths. Individual stages III-VI of Metridia nauplii occurred at 0 to 6 l-1, while Eucalanus nauplii were present at 0.1 to 9 l-1, depending on stage and depth. Nauplii III-IV of the genera Pseudocalanus and III-VI Microcalanus were usually present at less than 1 l-1. In 1992, 54 to 56% of the nauplii had body lengths of 150-350 μm which are typical of those found in stomachs of first-feeding pollock larvae. In 1993 corresponding estimates were 64 to 68%. Copepod nauplii with body lengths of 150-350 μm were generally present at 1 to 15 l-1, but at one station their counts exceeded 20 l-1.

TAXA COMPOSITION AND BIOMASS OF THE SURFACE-DWELLING CRUSTACEANS DURING SPRING PYCNOCLINE FORMATION IN AUKE BAY, SOUTHEASTERN ALASKA

ABSTRACT The crustacean-dominated zooplankton community that lives in the upper 5 m of water in one of southeastern Alaskas bays was monitored before and after spring pycnocline formation. Zooplankton abundance and wet weight biomass in the upper 5 m of the surface layer reached peak values of 50,000 m–3 and 2.5 g m–1, respectively. Surface populations were dominated by barnacle nauplii, with substantial contributions by the copepods Pseudocalanus spp., Acartia spp., and Centropages abdominalis. Barnacle nauplii were only a minor component of the zooplankton in whole water-column samples. Surface zooplankton abundance and biomass were higher at night than during the day in April and early May, prior to stabilization of the water column. The day versus night differences were primarily due to diurnal vertical migration by barnacle nauplii. Obvious diurnal differences in abundance and biomass of zooplankton at the sea surface were not detected after pycnocline formation. After pycnocline formation, copepod biomass in the upper 5 m was about 5 times higher than that of the integrated water column. This may explain why many young fishes congregate in the surface layer to feed.