Robert C. Bayer

The effects of soybean-based diets, with and without amino acid supplementation, on growth and biochemical composition of juvenile American lobster, Homarus americanus

Abstract The feasibility of feeding soy-based diets for the pound culture of the American lobster was investigated in a factorial study using diets (40% protein) containing various proportions of extruded-expelled, low-fat soybean meal (SBM) (0%, 25%, 50%, 75%, 87.5% and 100% of dietary protein) and fish meal (FM), with and without amino acid supplementation (arginine, leucine, methionine and tryptophan), in a 60-day feeding trial using late Stage 5 juveniles. The supplemental amino acids were added at levels to simulate the essential amino acid (EAA) profile of juvenile lobsters. The 0% SBM diet approximated salted fish and fish racks, the industry diet for pounded lobsters. A diet of fresh blue mussel, a component of the lobsters natural diet, was included for comparison. Supplementation and SBM levels of not more than 50% of dietary protein significantly resulted in higher body weight gains (BWGs) than diets without supplementation or with higher SBM levels. Survival was not significantly different for juveniles fed the supplemented diets and the non-supplemented diets containing FM. Juveniles fed the non-supplemented 100% SBM diet suffered early mortality. Supplementation significantly shortened molting cycles and was crucial for survival in juveniles fed the 100% SBM diet. Interactions between supplementation and level of dietary SBM on survival, BWG and duration of the molting cycle were significant. Growth performance of juveniles fed blue mussel were comparable to those of juveniles fed the supplemented 50% SBM diet. The levels (% of protein) of arginine, phenylalanine and tryptophan were significantly higher in juveniles fed the supplemented diets, while tyrosine, aspartate, glutamate and serine were significantly higher in juveniles fed the non-supplemented diets. Arginine levels in juveniles fed the supplemented diets were nearly twice those of juveniles fed the non-supplemented diets. Interactions between SBM level and supplementation on lobster amino acid profile were not significant. Supplementation and decreasing levels of dietary SBM (lower content of 18:2 n −6, the major polyunsaturated fatty acid (PUFA) in SBM) were associated with better growth and resulted in increasing proportions (% of total) of 20:5 n −3, 22:6 n −3 and n −3/ n −6 PUFA ratios in juvenile carcass. Based on weight gain, replacement of fish protein with SBM in practical diets at no more than 50% of dietary protein appears feasible, with multiple amino acid supplementation significantly enhancing growth performance.

The Lobster Parasite Anophryoides haemophila (Scuticociliatida: Orchitophryidae): Nuclear 18S rDNA Sequence, Phylogeny and Detection Using Oligonucleotide Primers

ABSTRACT. We have determined the nucleotide sequence of the nuclear gene encoding small‐subunit ribosomal ribonucleic acid of the ciliate Anophryoides haemophila, a parasite of the American lobster Homarus americanus. The gene is 1763 bp in length, and has a guanosine‐plus‐cytosine content of 43.9%. Inferred phylogenetic frameworks strongly support the monophyly of the scuticociliates, and suggest that order Scuticociliatida should be elevated to at least subclass rank. Oligonucleotide probes based on A. haemophila ssu‐rDNA can discriminate between DNAs of A. haemophila and other investigated hymenostome ciliates, and effectively prime polymerase chain reaction‐based detection of A. haemophila deoxyribonucleic acid against at least a 1600‐fold excess of total deoxyribonucleic acid from H. americanus.

The biochemical profiles of shell-diseased American lobsters, Homarus americanus Milne Edwards

The proximate % of dry weight , amino % of total amino acids and fatty acid % of total . . fatty acids profiles of tissues muscle, hepatopancreas, hemolymph and exoskeleton of American . lobster, Homarus americanus Milne Edwards affected with shell-disease, were compared with those of healthy, unaffected animals. Muscle tissues of affected lobsters had significantly lower levels of carbohydrate and the protein profile had significantly lower ratios of arginine, threonine, serine and total essential amino acids. However, the ratio of glycine was about 50% higher than in muscle tissues of healthy lobsters. Muscle tissues of affected lobsters had slightly higher ratios of 20:4ny 6 and 22:6ny 3. Affected lobsters had significantly lower hepatosomatic indices. Their hepatopancreas contained significantly higher levels of protein, 35% less lipid and 266% higher levels of ash, than healthy lobsters. The protein profile had significantly lower ratios of phenylalanine, threonine, and proline, but significantly elevated ratios of arginine. The ratio of 20:5ny 3, was about half that of healthy lobster hepatopancreas. Hemolymph of affected lobsters contained about 40% less protein, about 35% higher levels of ash and significantly higher histidine ratios in its protein profile than corresponding ratios in healthy lobsters. Ratios of phenylalanine and threonine were slightly but significantly lower and ratios of 18:2 ny 6 and 20:4ny 6 were significantly elevated than in healthy lobsters. The ulcerated exoskeleton of affected lobsters had significantly lower levels of total carotenoids and ash, and significantly higher moisture content and proportions of protein and lipid than the non-ulcerated parts, or the exoskeleton of healthy

Development of chemically mediated prey-search response in postlarval lobsters (Homarus americanus) through feeding experience

Postlarval lobsters were fed live amphipods (Gammarus oceanicus), soft clam spat (Mya arenaria), or frozen brine shrimp (Artemia salina) for five weeks in order to determine by behavioral bioassay if chemically mediated prey-search behavior is established by feeding experience. Chemosensory responses of predatorily naive lobsters to live clam and amphipod metabolites were low and erratic. After five weeks, amphipod-fed lobsters had developed strong responses towards amphipod metabolites but not clam metabolites. In contrast, clam-fed lobsters did not develop responses to either prey. Chemical fractionation of amphipod metabolites indicated that attractants were confined to the same fraction as for prey extracts, i.e., polar, low-molecular-weight compounds. Survival (80–90%) was similar for each diet group; growth was greatest for amphipod-fed lobsters (100%), followed by clam-fed lobsters (72%) and brine shrimp-fed lobsters (18%); and feeding rates increased for amphipod-fed lobsters and decreased for clam-fed lobsters. Coloration of lobsters indicated that only amphipod diet provided desirable pigments. Differences in ingestive conditioning results between clamfed and amphipod-fed lobsters may have been related to (1) clam metabolites being qualitatively or quantitatively less attractive than amphipod metabolites or (2) differences in the predisposition of lobsters to show ingestive conditioning to different prey and their associated metabolites as a function of quality of prey as a diet.

TRENDS IN MAINE SOFTSHELL CLAM LANDINGS

Abstract The soft-shell clam, Mya arenaria (L. 1758), has the highest landed value of Maine bivalves. Landings have been variable over the last century with current landings one third of their historical highs caused by low harvests in Eastern Maine. Diminished clam populations have been subjected to constant fishing pressure and heavy predation by green crabs apparently unchecked by winterkill. Clam stocks previously closed to harvesting because of pollution are now dug. Reduced breeding populations are tasked to produce a sufficient set to overcome offshore dispersal of larvae to repopulate flats on the coast of Maine. On-bottom and off-bottom sampling found few clam larvae in Eastern Maine. Recovery of the fishery will require reestablishment of breeding stocks.

Temporal changes in release rates and quality of lobster (Homarus americanus) feeding attractants from herring (Clupea hareng us) baits

Primary amine release rates of various herring preparations (frozen, fresh, and 20% salt) were determined over a 45h period in order to evaluate characteristic chemical‐release profiles of baits for lobsters (Homarus americanus). Over the first 5.5h, salted herring had high but declining amine release rates. A similar, less pronounced pattern of amine release was observed for frozen herring while that of fresh herring remained stable and low. After 12h, the release rates of all preparations were equivalent and low. A behavioral bioassay of post‐larval lobsters was used to determine the level of directed food‐search response to frozen and salted herring leachates collected over the 45h period and adjusted to equimolar amine concentrations. No differences in attractiveness among the two bait types were observed at any one time of leaching. Attractants were confined to polar, primary amine containing fractions. There was, however, a decrease in response to the leachates with time suggesting that decay advers...

Safety and efficacy of oxytetracycline for control of gaffkemia in the American lobster (Homarus americanus)

Abstract Among lobsters ( Homarus americanus ) held in captivity, periodic outbreaks of gaffkemia, a bacterial disease caused by the bacterium Aerococcus viridans , results in severe mortality. This study demonstrated the safe and effective use of oxytetracycline (OTC) for the control of this disease. A dose titration study was done by feeding OTC-supplemented diets containing 0.5, 1.1 or 2.2 mg OTC g −1 diet or an unsupplemented diet to four replicate groups of 15 lobsters per treatment. The lobsters were challenged by infection with Aerococcus viridans . Mortality was 100% for the non-medicated group and 68, 33 and 15% for lobsters fed 0.5, 1.1 and 2.2 mg OTC g −1 diet, respectively. A second study used a more natural spread of infection by placing one infected lobster in each replicate. Four hundred and fifty lobsters were placed in 30 crates and fed on unsupplemented diet or one containing 1.1 or 2.2 mg OTC g −1 diet. Mortality from gaffkemia was 78% in the lobsters that consumed the non-medicated diet compared with 13 and 2% for those receiving 1.1 or 2.2 mg OTC g −1 diet, respectively. Target species safety was studied by feeding lobsters with 11, 27.5 or 55 mg OTC g −1 diet for a 15-day period. There was no mortality during this period. The lobsters fed the two diets highest in OTC were killed and a post-mortem examination revealed one lobster with a chronic inflammatory response in the mid-gut. Residue analysis was done on lobsters that were fed 1.1 or 2.2 mg OTC g −1 diet for 10 days. Muscle, the primary tissue, was free of residue at 14 or 28 days in trials conducted at ambient temperature of 15–19 or 14–15°C, respectively. The mid-gut was free of residue after 28 days in the warmer temperature range and contained less than 0.1 mg OTC g −1 tissue in the second trial.

Studies on the Mineral Requirements of the Adults American Lobster

Abstract In a series of laboratory and field studies, the effects of dietary mineral supplements were tested on adult lobsters (Homants americanus). Both semipurified diets and diets formulated from commercial ingredients were used. Results of these studies indicated that the optimum ratio of calcium and phosphorus (Ca:P) for adult lobsters was about 1:1, which agrees with optimum levels determined previously for juvenile lobsters. Results also indicated that added mineral supplements are of no particular benefit to adult lobsters in diets formulated for commercial use in pounds, as long as the ash present in the commercial ingredients has a Ca: P ratio near 1:1.

Attraction of predatorily naive postlarval lobsters to extracts of metabolites of common prey:Mytilus edulis, Mya arenaria, Cancer irroratus, andAsterias vulgaris

Postlarval lobsters (4th–7th stage) exclusively fed frozen brine shrimp (Artemia saline) were assayed for food-search response to extracts and metabolites from four common prey: soft clams (Mya arenaria), blue mussels (Mytilus edulis), rock crabs (Cancer irroratus), and sea stars (Asterias vulgaris). Concentrations of soluble primary amines, protein, and ammonia in prey tissues and metabolites were determined. No significant responses were observed for any prey metabolites diluted to 1 and 10%, while onlyA. vulgaris evoked a significant response at full strength, suggesting that predatorily naive lobsters have yet to develop more pronounced chemosensory responses shown by field-collected lobsters. Removal of protein with retention of small-molecular-weight polar molecules did not appear to affect response to prey extracts. EC50s, as micromoles per liter amines, computed from prey extract dose-response curves indicate differences per unit amine between prey extracts, withA. vulgaris extract more potent as an attractant than either bivalve extract.C. irroratus extract was equally attractive as the other three extracts. Ammonia levels excreted into seawater over 3 hr were similar for all prey species, while soluble primary amines and proteins were undetectable. Ammonia and protein per gram whole prey varied significantly between extracts of prey species, while primary amines were similar. Lobsters may be attracted preferentially to carrion species with higher concentrations of amines and/or higher potency of attractants per unit amine.

A refractometric method of determining serum protein concentration in the American lobster

Abstract A rapid simple method of quantitating serum protein concentration in lobster hemolymph was developed using a Uricon ® specific gravity refractometer. A correlation coefficient of r = 0.985 (n = 21) was observed in calculating serum protein concentration, Y = 5449.417X – 7295.321 ( Y = serum protein concentration (mg/ml), X = refractive index). This procedure provides a nondestructive field method to assess a lobsters physiological state without returning samples for laboratory analysis.