Lobster research integrated: From biology to management

This thematic issue reflects our Journal's interest in publishing one or two such thematic issues per year on a regular basis. In this way we hope to raise our readers’ awareness about significant outcomes from joint meetings, expeditions or projects devoted to interesting and timely topics in marine biology. And, we also want to motivate colleagues to submit proposals for future thematic issues in Marine Biology Research (see also: Thematic Issues in Marine Biology Research ) accessible at the journal website (http://www.tandfonline.com/mbr).

At three-yearly intervals, the International Conference & Workshop on Lobster Biology & Management (ICWL) summarizes the state of the art lobster research and management. The 9th ICWL at Bergen continued the tradition established through the previous eight conferences, with high-quality scientific oral and poster presentations mingling scientists, academia, managers, and industry representatives of over 150 attendees from more than 20 countries. From the rich spectrum of conference contributions, 11 papers have been selected to elucidate a mutual close dependency of biological research and lobster conservation and management issues.

Lobsters are top predators within worldwide benthic domains, inhabiting mostly rocky bottom but soft sediments as well, often in highly productive coastal waters and shelf seas. This refers to both the clawed lobsters of northern cooler waters and the clawless rock lobsters found closer to the equator. Their positions at the top levels of food webs give them a controlling and indicator function in changing ecosystems, driven by climatic changes as well as increasing constraints through fishery.

Group picture of ICWL Bergen attendees at bow of SS Str. Lehmkuhl.

Management of spiny lobster populations in the Caribbean and around Australia appears traditionally well-supported, probably as a consequence of the early radical depletion by uncontrolled fishery. Examples of spiny lobster research demonstrate particularly well the intimate relationship of biological studies being the basis for conservation measures. The reciprocal nature of environmental control and fishery impact may be further shown by the strong difference of recent population development in the two Homarus species: the huge catch numbers along the Eastern North Atlantic coasts of Homarus americanus H. Milne Edwards, 1837 have been increasing over the last decade, whereas its European counterpart, Homarus gammarus (Linnaeus, 1758), is definitively decreasing in numbers having even led to the collapse of some lobster-dominated communities (Agnalt et al. 2007). Generally, to disentangle causes and effects of ecological and man-induced changes remains a challenge. The large and therefore charismatic lobster species help in comparative and causal analysis, often directly embedded in ecosystem approaches, relating in turn to sea management issues. Larger-scale population studies are flanked by intrinsic research on behavioural, physiological or genetic traits of adaptability in the lobster. The conference has always served as a discussion and exchange forum to link these broad approaches and to identify gaps in the science which can be filled by cooperation. The final contribution of the series shows this clearly in an exemplary way.

From the Bergen ICWL the following topics have generated this thematic issue and we are happy that prominent international authors from Australia, Canada, Germany, Iceland, Italy, Mexico and USA have contributed. The objects of study span from the small mud-dwelling Norway lobster Nephrops norvegicus (Linnaeus, 1758) to the giant eastern rock lobster Sagmariasus verreauxi (H. Milne Edwards, 1851) of the east coast of Australia and from physiological and adaptive traits to an example of successful management of a specific population.

The series starts with a paper on the Norway lobster where moult staging is proposed as a pre-requisite for ecological reasoning (Philip & Marteinsdottir 2013; contribution 1) followed by an article on the European clawed lobster H. gammarus, reporting temperature effects on moulting and motility with a view to climatic change and management measures (Schmalenbach & Buchholz 2013; contr. 2). The first of four contributions on the American lobster H. americanus demonstrates the fine structure of the lobster's cuticle as an interface to the environment (Kunkel & Jercinovic 2013; contr. 3) followed by a paper on intraspecific recognition and communication (Gherardi et al. 2013; contr. 4) leading to an encompassing study of benthic recruitment (Wahle et al. 2013; contr. 5) and concluding with a behavioural study which has consequences for sampling and population assessment (Watson & Jury 2013; contr. 6). Five papers on spiny lobsters from the Caribbean and Australia begin with a record of mechanisms of mate choice (Robertson & Butler 2013; contr. 7), followed by a behavioural study of seasonal aggregation including a model for management (Briones-Fourzán et al. 2013; contr. 8), a tag and release programme evaluated by a model feeding into management (Ley-Cooper et al. 2013; contr. 9), larval development and stock management (Linnane et al. 2013; contr. 10), and finally a comprehensive case study of interfacing research and support of governmental stock management (Montgomery & Liggins 2013; contr. 11).

We consider it a major accomplishment to go beyond simply publishing a suite of conference papers in making a selection of our recent findings available to a larger audience collected in one thematic issue of Marine Biology Research. In particular, the thematic issue will make a strong point that the lobster is not only a highly priced commercial target but a particularly suitable interface and key to very different marine environments in a changing world. The following, brief extracts of the 11 contributions (numeration from above) highlight the increase in knowledge of the species biology and life history to be used for resource management including aquaculture and stock enhancement.

1.	Crustacean life is dominated by the moult cycle, a series of regular physiological and behavioural changes that enable the organism to grow. A method is described to determine the individual stages in the cycle of the Norway lobster Nephrops norvegicus. The technique is used to investigate changes in haemolymph total protein and haemocyanin across the cycle. Peaks are detected in both parameters at the final stage of intermoult and during active pre-moult, suggesting an increase in metabolic activity. In addition to validating the moult staging method, the results highlight the importance of considering the underlying physiology of lobsters in either experimental or ecological studies. In fact, analogous to medical blood tests, haemolymph analysis yields valid results with regard to determining the performance and health of crustacean development in the field or in aquaculture.
2.	The effect of seasonal temperature on the behavioural and physiological activity of European lobster Homarus gammarus was examined, observing the timing of moulting and locomotory activity in juvenile lobsters maintained at increasing temperatures under standardized laboratory conditions. Significant responses to seasonal temperatures were found with clear temperature thresholds. The knowledge about the temperature-dependent activity of lobsters may be helpful to explain behaviour in the field and in assessing the chances of a future stock-enhancement programme.
3.	Various carbonate apatite formulae contribute to discrete cuticle structures participating in protective functions of the integument of the American lobster Homarus americanus. A schematic model of the cuticle emphasizes regional diversity of a composite cuticle suggesting mineral function. An outer calcite crystalline layer provides a dense barrier that dissolves slowly through an intact epicuticle, providing an external alkaline unstirred layer inhibitory to bacterial physiology. Superficial injury to the epicuticle and calcite layer provides a stronger flush of alkalinity from bared calcite or deeper rapidly dissolving amorphous calcium carbonate, generating a concerted general-immune response by increasing alkalinity of the unstirred layer. Knowledge on such mechanisms is important as recently bacterial shell disease reduced local lobster stocks substantially.
4.	The American lobster is able to recognize the identity of conspecifics. To be recognized, individuals should bear unique phenotypic traits that are unlikely to be confused in the crowd where colour and morphological features in individuals facilitate recognition. The night active lobster uses mainly olfaction to evaluate surroundings and conspecifics, i.e. mates, and prey. Apparently, exploration is flanked by eyesight. Olfaction in turn is easily hampered by xenobiotics.
5.	Early benthic-phase lobsters are evasive. Passive collectors were used and compared to other methods. Geographical patterns of young-of-year and older juvenile American lobster abundance were found that have emerged at an unprecedented geographic scale from coastal Newfoundland to southern New England, as well as several offshore locations, by virtue of an international collaboration. Spatial correlations identified consistent settlement ‘hot spots’ that are most likely determined by ocean circulation. The coincidence of lobster recruits and suspected predators or competitors, such as fishes and crabs, suggests that such species interactions are weak, and are unlikely to bias collector results.
6.	Lobster traps were fished concurrently with SCUBA surveys conducted to determine American lobster densities along the New Hampshire coast, USA. It was found that while standard commercial traps are a reasonable indicator of pre-recruit lobster abundance under some conditions, but due to the behavioural characteristics of lobsters, the relationship between catch and density is limited, particularly at higher densities and for legal-sized lobsters. A better understanding of the behavioural mechanisms that influence catch could improve the use of catch data to predict abundance.
7.	An exploration of how mate size influences mating dynamics in the spotted spiny lobster Panulirus guttatus (Latreille, 1804), a philopatric species that lives on shallow and often isolated coral reefs in the Caribbean where choice of mates can be limited, was carried out. The availability and size of male and female lobsters in a series of laboratory experiments was varied. It was found that for species like P. guttatus that dwell in patchy habitats with limited mate availability, the optimal strategy for mate choice is context-dependent, although not without cost to the largest females.
8.	The spotted spiny lobster P. guttatus is an obligate reef-dweller that reproduces year-round and exhibits a low degree of gregariousness. Yet, previous laboratory studies revealed that these lobsters were significantly attracted to conspecific scents during a period of ‘high reproductive activity’ (HRA,>50% of ovigerous females in the population) but not during a period of ‘low reproductive activity’ (LRA,<40%), suggesting that seasonal changes in aggregation increase reproductive opportunities for these lobsters. This hypothesis was tested in the field and a model applied. Although results were modulated by the local density of lobsters on each patch, they generally support the hypothesis that seasonal aggregation increases reproductive opportunities.
9.	The fishery for Caribbean spiny lobster Panulirus argus (Latreille, 1804) represents the main income within the Biosphere Reserve of Sian Ka'an, Mexico. Commercial catch rates were examined and a wide size range of lobsters were tagged in order to examine fishing mortality rates and movement patterns. The Brownie model indicated that exploitation rates within this bay area is high (>94%). Changes in CPUE and catchability throughout the season explain how the ‘casita/campo’ system allows for a seasonal replenishment of juveniles and adults and this has kept the landings relatively stable for the past decade.
10.	The commercial fishery for southern rock lobster Jasus edwardsii (Hutton, 1875) is South Australia's most valuable fishery resource. Over the past decade, recruitment to the fishable biomass has decreased, which has translated to declines in commercial catch rates. Puerulus monitoring has been undertaken since 1996, with the period from settlement to recruitment estimated at ~4 years. In 2002, 2005 and 2006, spikes in settlement were recorded, which were predicted to enter the fishery as recruitment pulses in 2006, 2009 and 2010, respectively. The study highlights the importance of management decisions that conserve recruitment pulses in order to sustain lobster resources on which fisheries depend.
11.	Catch per unit effort in the fishery for eastern rock lobster Sagmariasus verreauxi peaked in 1971–72 and then declined until 1992–93. A management package consisting of individual catch quotas, restricted entry and a legal minimum length was imposed upon the fishery. The effectiveness of these management measures to rebuild the eastern rock lobster population has been monitored annually through data collected from surveys of puerulus larval abundance, fishery-independent surveys, a compulsory logbook, observer surveys and biological studies. Total, exploitable and spawner biomass have all increased, with spawner biomass now estimated to be above 25% of the pre-exploited level. The relative abundance of recruits (puerulus larvae) to the population is also increasing. As a result, the stock is considered to be rebuilding and the resource now supports a viable fishery with a lucrative share price.

Finally, the editors would like to express their gratitude to our subject editors Aril Slotte (Fisheries Biology) and Marsh Youngbluth (Macrozooplankton) who recently left us, for having served Marine Biology Research for periods of nearly eight and six years, respectively. And, we want to cordially welcome our new subject editor Christopher P. Kenaley (Fish Systematics)!