Pacific Science (1999), vol. 53, no. 4: 361-366 © 1999 by University of Hawai'i Press. All rights reserved Some Preliminary Findings on the Nutritional Status of the Hawaiian Spiny Lobster (Panulirus marginatus)l FRANK A. PARRISH2 AND THERESA L. MARTINELLI-LIEDTKE3 ABSTRACT: Data on the nutritional status of spiny lobster (Panulirus margin­ atus) were collected on the commercial trapping grounds of Necker Bank, Northwestern Hawaiian Islands, in the summers of 1991, 1994, and 1995. Gly­ cogen levels measured in abdominal tissue of intermolt males were used as an index of nutritional health of the field population. The range of glycogen sampled from wild lobster was less than half the level measured in captive lob­ ster fed to satiation in a previous study. An analysis ofcovariance identified sig­ nificant interannual and spatial effects explaining 46% of the variance in the sample ofwild lobsters. Most significant was a decline in lobster glycogen levels between samples collected in 1991 and 1994-1995. Seasonal influences on lob­ ster nutrition are unknown and were identified as an obvious direction for future ecological research. NUTRITIONAL CONDITION OF lobster, as as­ found to be the best index of nutritional sta­ sessed in the field, could be a valuable tool to tus tested for this species (Figure 1). Tests of provide insight to physiological response of within-lobster variability indicated that a lobster to environmental constraints. The single sample per lobster was adequate for nutritional status ofpa1inurids in the wild has analysis (Martinelli 1993). The positive linear been little studied (Kanciruk 1980). Studies relationship between recency of feeding and of lobster nutrition have centered on needs lobster glycogen concentration provided a associated with rearing and aquaculture relational indicator that could be used to (Kanazawa 1994). Only recently have labo­ document spatial or temporal variation in the ratory trials of nutritional indices been ap­ nutritional status of field populations. plied to address ecological issues (Moss 1994, Blood glucose concentration is controlled Robertson et al. 1996). The work reported by homeostatic mechanisms in many deca­ here used an index of lobster nutritional sta­ pod species (Heath and Barnes 1970, Dall tus on a managed field population to provide 1974). Glucose is held in reserve deposits as some preliminary data on field nutrition and glycogen that can be depleted during periods to discuss it in relation to a period of popu­ of reduced food consumption to maintain lation growth. blood glucose concentrations near normal A number of nutritional indices were levels. Although the digestive gland is con­ evaluated by Martinelli (1993) using Pan­ sidered the main organ for storage of nutri­ ulirus marginatus in controlled, replicated, tional reserves in decapods, its importance as month-long laboratory trials. The concentra­ a storage organ relative to muscle tissue is tion of glycogen in abdominal muscle was variable among species (Armitage et al. 1972, Dall 1981, Barclay et al. 1983, Whyte et al. 1986). When P. marginatus is nutritionally 1 Manuscript accepted 29 January 1999. stressed, it catabo1izes abdominal muscle 2 Honolulu Laboratory, Southwest Fisheries Science glycogen reserves (Martinelli 1993). Storage Center, National Marine Fisheries Service, NOAA, 2570 of glycogen in abdominal muscle, like most Dole Street, Honolulu, Hawai'i 96822-2396. physiological processes in lobster, is influ­ 3 U.S. Geological Survey, Biological Resources Divi­ sion, Columbia River Research Laboratory, 5501A enced by molt stage (Heath and Barnes Cook-Underwood Road, Cook, Washington 98605. 1970). 361 362 PACIFIC SCIENCE, Volume 53, October 1999 20 ,---------------, ment cruises. The annual cruise revisits es­ 18 tablished stations in the NWHI and conducts standardized trap fishing. The annual assess­ 16 ment was conducted just before the commer­ 0;14 cial season, which was open July-December. C> This ensured that lobster sampled had not .s 12 been previously disturbed by the baiting and :ii 10 0) trapping activities of other fishing vessels. In o 8 o this paper we make temporal and spatial >. comparisons of lobsters from the assessment a 6 • Fed lobsters y=13.6-0.005x, 2 stations of Necker Bank (Figure 2). Stations 4 P=0.95, r =0.001, n=42 were selected to represent the range in types 2 0 Starved lobsters y=11.7-0.214x, of bottom habitat that had been documented 2 r O+---'--,...::..:.c:...:....:.;..:-----=-~e..:..:.-.:,.:....-~-~-__lP=0.001, =0.91, n=39 in previous surveys (parrish and Polovina o 5 10 15 20 25 30 1994). Days of Treatment Lobster glycogen concentrations were sampled at stations A and B in July 1991, FIGURE 1. Laboratory trials of lobster glycogen con­ May 1994, and June 1995. For the 1994 and centration plotted relative to days of treatment. Each 1995 collections, two additional stations (C data point represents multiple lobster (mean = 7, and D) were included. At each station, the maximum = 9). Filled circles are lobster fed daily and open circles are lobster starved. Confidence intervals glycogen levels of at least 25 male lobster (95%) are included for both treatments. A consistent representing the size range of the catch were and significant decline is measurable using the glycogen tested. To avoid potential influence of molt assay to assess starved lobsters. (Source: Martinelli 1993) stage on glycogen level (Lipcius and Herrn­ kind 1982), the molt stage of the males was determined using Lyle and MacDonald's The commercial stock of P. marginatus (1983) technique to ensure that only lobsters occurs in the remote Northwestern Hawaiian in intermolt were included in the analysis. A Islands (NWHI) and has been fished ex­ sample of abdominal muscle tissue was ex­ clusively by commercial vessels beginning in tracted from each lobster and analyzed for the early 1970s. Consequently, all fishery glycogen content (Martinelli 1993). Females effort is documented. In 1991, catch per unit were excluded from all analyses to remove of effort (CPUE) dropped to rougWy half the any possible effects on nutrition associated level used to designate optimum sustainable with egg production (Hermkind 1980). yield (i.e., one lobster per trap), prompting Standard analysis of covariance (AN­ temporary closure of the fishery. Since then, COYA) was used with the glycogen data to fishing has been restricted by quota and sea­ assess interannual and spatial effects and son to permit the stock to recover (Haight effects of lobster size. Because of the unbal­ and DiNardo 1995). All glycogen sampling anced design associated with absence of occurred during the period of stock recovery. samples for stations C and D in 1991, the Sampling during a period of increasing pop­ ANCOVA was rerun excluding the 1991 ulation density provided an opportunity to data. look for an expected density-dependent de­ cline in lobster condition using the glycogen index. RESULTS Eleven of the collected lobster were ex­ cluded from analysis because they were in MATERIALS AND METHODS premolt condition. Lobster carapace length Lobster were collected as part of the Na­ ranged between 39 and 110 mm. Plotting the tional Marine Fisheries Service (NMFS) size frequency of lobster measurements in­ Honolulu Laboratory's (HL) lobster assess- dicated that distributions were similar for all Nutritional Status of the Hawaiian Spiny Lobster-PARRISH AND MARTINELLI-LIEDTKE 363 164°50 164°25 23°50 ---- "10 --- 0 /)-;,, \ I \ I I I I I {~:' Necker Is, \ \ \ \ \ \ \ B \ Midway c '- -"" -----­ Ii> Atoll •• Q •• ~, ""'" NECKER BANK 23°30 NORTHWESTERN HAWAIIAN ISLANDS MAIN PACIFIC OCEAN HAWAIIAN iSLANDS III I lBO' 175' 170' 165' 180' 155' FIGURE 2, Hawaiian Archipelago with an inset of Necker Bank indicating the locations of the four trapping sta­ tions. samples except one (mean CL 8 em) (Figure 12 . 3). The exception was the 1991 sample at . 10 . station A, which provided smaller lobsters Ci . ' . (mean CL 4.5 em). The ANCOVA identified -Cl 8 . .' significant temporal and spatial effects ex­ S ~ .. c . plaining 46% of the sample variance (Table Q) 6 '" .' Cl ",., .. 1). No size-specific differences were identi­ 0 ... • ..-•..... (,) i·..... fied. Lobsters collected in July 1991 had sig­ >. 4 .. .. l':'.' .. .. '" .I",t-"~•• nificantly better nutritional condition (higher (; ... , .. 2 .- ;;I~""... , .. ~ ...... glycogen) than the samples of May 1994 and •..'l'., ~.. .. June 1995 (Duncan multiple range test, 0 P < 0.01, df = 279). An a posteriori test of 4 6 8 10 12 spatial effects grouped two stations (A and Lobster carapace length (em) D) as having lobster in significantly better FIGURE 3. Plot of glycogen levels versus carapace condition than at the other two stations length of each lobster sampled. Samples collected in (Duncan multiple range test, P < 0.01, df = 1991 are indicated with triangles. Circles indicate sam­ 279). The 1991 data were then removed to ples collected during 1994 and 1995. 364 PACIFIC SCIENCE, Volume 53, October 1999 TABLE 1 ANCOVA TABLE OF LoBSTER GLYCOGEN LEVELS RELATIVE TO LOBSTER SIZE, YEAR OF COLLECTION, AND STATION VARIABLE SS df MS FSTATISTIC PVALUE Size 0.00018 1 0.0001 0.00 0.99 Year 349.4 2 174.7 59 0.0001 Station 125.8 3 41.9 14.1 0.0001 balance the sampling design and fully focus The reason for the significant drop in gly­ the analysis on the spatial effects. Without cogen levels between 1991 and 1994-1995 is the 1991 data, significance for station A dis­ unknown. The change coincides with the appeared, and data from station A were closure of the fishery and regrowth of the lumped with those from stations Band C in stock (Haight and DiNardo 1995). The stock overlapping classifications (Duncan multiple recovery leveled in 1994 and 1995 and the range test, P < 0.01, df = 235). Station D fishery continues to be exploited near opti­ alone was identified as having lobsters in sig­ mum sustainable yield (e.g., CPUE of 1.0) nificantly better condition.