Kari L. Lavalli

Cooperative defence and other benefits among exposed spiny lobsters: inferences from group size and behaviour

Caribbean spiny lobsters show strikingly coordinated queuing behaviour and resting, outward-facing radial formations, especially during mass migrations when large numbers cross shelter-poor substrate in daylight. The close association of individual lobsters during these behaviours could be due to chance or some benefit of association such as dilution (and associated selfish-herd effects), group vigilance, cooperative defence, and/or drag reduction during migration. To infer probable beneficial functions, we examined the frequency distributions of individuals and groups using a seven-year set of field data and additional behavioural observations in large seawater enclosures. Group size distributions were not significantly aggregated in dens during the non-migratory period but became highly aggregated during migration. The group size distributions of lobsters initially leaving dens and those observed moving in the open were statistically different from one another, indicating that group sizes at each of these steps in the migration are not simply the result of previous group sizes. The distribution of group sizes suggests that, during movement in the open, dilution, vigilance, cooperative defence, and/or drag reduction may all favour the formation of queues. During resting in the open, dilution, vigilance, and cooperative defence may continue to favour individuals that remain in formation within the group.

The Biology and Fisheries of the Slipper Lobster

INTRODUCTION Introduction to the Biology and Fisheries of Slipper Lobsters, K.L. Lavalli and E. Spanier BIOLOGY OF SLIPPER LOBSTERS Taxonomy and Evolution, W.R. Webber and J. Booth Genetics of Slipper Lobsters, A.M. Deiana, A. Libertini, A. Cau, R. Cannas, E. Coluccia, and S. Salvadori Early Life Histories of Slipper Lobsters, H. Sekiguchi, J.D. Booth and W.R. Webber Factors Important in Larval and Postlarval Molting, Growth, and Rearing, S. Mikami and A.V. Kuballa Feeding Morphology and Digestive System of Slipper Lobsters, D. Johnston Behavior and Sensory Biology of Slipper Lobsters, K.L. Lavalli, E. Spanier, and F. Grasso The Mineralization and Biomechanics of the Exoskeleton, F.R. Horne and S.F. Tarsitano Growth of Slipper Lobsters of the Genus Scyllarides, M. Bianchini and S. Ragonese Directions for Future Research in Slipper Lobster Biology, E. Spanier and K.L. Lavalli FISHERY BIOLOGY OF SLIPPER LOBSTERS Observations on the Ecology of Scyllarides aequinoctialis, S. nodifer, and Parribacus antarcticus and a Description of the Florida Scyllarid Lobster Fishery, W.C. Sharp, J.H. Hunt, & W. H. Teehan The Northwestern Hawaiian Islands Lobster Fishery: A Targeted Slipper Lobster Fishery, G. DiNardo and R. Moffitt The Biology of the Mediterranean Scyllarids, D. Pessani and M. Mura Biology and Fishery of the Galapagos Slipper Lobster, A. Hearn, V. Toral-Granda, C. Martinez, and G. Reck Biology and Fishery of Slipper Lobster, Thenus orientalis, in India, E.V. Radhakrishnan, M.K. Manisseri, and V.D. Deshmukh Biology and Fishery of the Bay Lobster, Thenus spp., C.M. Jones Fishery and Biology of Commercially Exploited Australian Fan Lobsters (Ibacus spp.), J.A. Haddy, J. Stewart, and K.J. Graham Slipper Lobster Fisheries-Present Status and Future Perspectives, E. Spanier and K.L. Lavalli List of Contributing Authors List of Reviewers for Chapters Index

Collective defense by spiny lobster (Panulirus argus) against triggerfish (Balistes capriscus): effects of number of attackers and defenders

Abstract Migrating queues of Caribbean spiny lobsters, Panulirus argus, suffer attacks during daylight by variable numbers of triggerfish they encounter on patch reefs. When threatened, lobsters assemble into outward facing, rosette‐like groups, remain coherent in their spacing, and defend themselves by parrying with their spinous antennae. In 90‐min field tethering trials involving predatory grey triggerfish (Balistes capriscus), solitary lobsters were subdued 44% of the time whereas grouped lobsters suffered only minor bites; triggerfish present numbered from 1 to 23. Victims of fish attack were significantly smaller than survivors in the field trials. Although attack/defense ratios did not differ between solitary and grouped lobsters, fish behaviours towards such different groups did differ with more bite attempts/bites being directed towards solitary lobsters. In a series of experiments in large seawater enclosures, we pitted 1, 3, 5, 10, or 20 free‐moving lobsters against 2 or 5 grey triggerfish, all of which had previously killed lobsters. We hypothesised that larger fish numbers would be more effective in subduing the prey independent of lobster group size, but that lobsters in larger groups would benefit by a higher per capita survival rate, as compared with smaller groups. We found that per capita mortality declined with lobster group size, but remained the same statistically whether there were two or five triggerfish. Triggerfish interference may have played a role in reducing the effect of greater numbers of attackers.

Does gregariousness function as an antipredator mechanism in the Mediterranean slipper lobster, Scyllarides latus?

The possible antipredation benefits of group living have been difficult to study in species where the size and incidence of groups are beyond the investigator’s control. A field test with tethered Mediterranean slipper lobsters, Scyllarides latus, revealed that attack and capture rates for solitary individuals did not differ significantly from those for grouped individuals after either 3 or 24 h of exposure to potential predators. Although predator attack rates on grouped and solitary lobsters also did not differ after 3 h, they were significantly higher on groups than on solitary lobsters after 24 h. Differences in fish behaviour during the first hour of lobster exposure suggest that confusion effects played a role only initially and, presumably, conferred a short-lived advantage on clumped prey. Confusion effects were represented by a higher frequency of passes and reapproaches for fish concentrating on grouped lobsters and a lower frequency of bites. Attacks were more directed for fish concentrating on solitary lobsters. With increasing exposure time, however, groups may have served to facilitate predation because triggerfish (Balistes carolinensis) were equally successful at capturing grouped and solitary lobsters.

First record of an early benthic juvenile likely to be that of the Mediterranean slipper lobster, Scyllarides latus (Latreille, 1802)

To date no nisto and/or live juvenile of the Mediterranean slipper lobster, Scyllarides latus (Latreille, 1802), has been found despite intensive sampling efforts. In the early 1900s, a tiny preserved specimen, almost certainly of this species, with carapace length of 11.7 mm, sampled in Reggio Calabria, southern Italy, was captured and deposited in the Zoological Museum of Turin. This early scyllarid juvenile, likely a recent benthic recruit, varies somewhat from the adult form of the local Mediterranean species, S. latus, by having a carapace width that is greater than the carapace length and by having more prominent tubercles than adults. These same features also have been noted in nistos of a few other non-Mediterranean Scyllarides species, especially those of S. nodifer (Stimpson, 1866). Although the collection information for this specimen was incomplete, additional data on habitats of sub-adults of S. latus enable the construction of a hypothetical recruitment scenario. It is likely that S. latus larvae drift large distances for many months in the pelagic before settling as nistos in deeper water where they are possibly more protected against predators and develop to small juveniles before returning to the shallower adult grounds as migrating larger juveniles or sub-adults.

PUBLICATION IN THE JOURNAL OF CRUSTACEAN BIOLOGY

(FRS, correspondence: jcb@whidbey.com) General Editor, P.O. Box 1569, Langley, Washington 98260, U.S.A.; (STA) P.O. Box 14-901, Kilbirnie, Wellington, New Zealand; (KAC) Department of Integrative Biology, Brigham Young University, Provo, Utah 84602-5181, U.S.A.; (FG) Biologia Animale e Genetica, Università degli Studi di Firenze, Via Romana 17, I-50125, Firenze, Italy; (MJG) Lake Biwa Museum, Oroshimo 1091, Kusatsu, Shiga 525-0001, Japan; (KLL) CGS, Division of Natural Science, Boston University, Boston, Massachusetts 02215, U.S.A.; (GP) Museum Victoria, G.P.O. Box 666, Melbourne, Victoria 3001, Australia; (DCR) EcoAnalysts, Inc., 707 Dead Cat Alley, Woodland, California 95695, U.S.A.; (GS) Humboldt-Universität zu Belin, Institut für Biologie/ Vergleichende Zoologie, Philippstraße 13, D-10115 Berlin, Germany; (TS) U.S. Fish and Wildlife Service, 620 S. Walker St., Bloomington, Indiana 47403-2121, U.S.A.; (ST) Department of Biology, University of Alaska Southeast, 11120 Glacier Highway, Juneau, Alaska 99801, U.S.A.; (MW) Department of Biology, Texas A&M University, College Station, Texas 77843, U.S.A.

A Noninvasive Method For In situ Determination of Mating Success in Female American Lobsters (Homarus americanus)

Despite being one of the most productive fisheries in the Northwest Atlantic, much remains unknown about the natural reproductive dynamics of American lobsters. Recent work in exploited crustacean populations (crabs and lobsters) suggests that there are circumstances where mature females are unable to achieve their full reproductive potential due to sperm limitation. To examine this possibility in different regions of the American lobster fishery, a reliable and noninvasive method was developed for sampling large numbers of female lobsters at sea. This method involves inserting a blunt-tipped needle into the females seminal receptacle to determine the presence or absence of a sperm plug and to withdraw a sample that can be examined for the presence of sperm. A series of control studies were conducted at the dock and in the laboratory to test the reliability of this technique. These efforts entailed sampling 294 female lobsters to confirm that the presence of a sperm plug was a reliable indicator of sperm within the receptacle and thus, mating. This paper details the methodology and the results obtained from a subset of the total females sampled. Of the 230 female lobsters sampled from Georges Bank and Cape Ann, MA (size range = 71-145 mm in carapace length), 90.3% were positive for sperm. Potential explanations for the absence of sperm in some females include: immaturity (lack of physiological maturity), breakdown of the sperm plug after being used to fertilize a clutch of eggs, and lack of mating activity. The surveys indicate that this technique for examining the mating success of female lobsters is a reliable proxy that can be used in the field to document reproductive activity in natural populations.