Causes of decoupling between larval supply and settlement and consequences for understanding recruitment and population connectivity

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Experimental Marine Biology and Ecology 392 (2010): 9-21, doi:10.1016/j.jembe.2010.04.008.Marine broadcast spawners have two-phase life cycles, with pelagic larvae and benthic adults. Larval supply and settlement link these two phases and are crucial for the persistence of marine populations. Mainly due to the complexity in sampling larval supply accurately, many researchers use settlement as a proxy for larval supply. Larval supply is a constraining variable for settlement because, without larval supply, there is no settlement. Larval supply and settlement may not be well correlated, however, and settlement may not consistently estimate larval supply. This paper explores the argument that larval supply (i.e., larval abundance near settlement sites) may not relate linearly to settlement. We review the relationship between larval supply and settlement, from estimates and biases in larval supply sampling, to non-behavioral and behavioral components, including small-scale hydrodynamics, competency, gregarious behavior, intensification of settlement, lunar periodicity, predation and cannibalism. Physical and structural processes coupled with behavior, such as small-scale hydrodynamics and intensification of settlement, sometimes result in under- or overestimation of larval supply, where it is predicted from a linear relationship with settlement. Although settlement is a function of larval supply, spatial and temporal processes interact with larval behavior to distort the relationship between larval supply and settlement, and when these distortions act consistently in time and space, they cause biased estimates of larval supply from settlement data. Most of the examples discussed here suggest that behavior is the main source of the decoupling between larval supply and settlement because larval behavior affects the vertical distribution of larvae, the response of larvae to hydrodynamics, intensification of settlement, gregariousness, predation and cannibalism. Thus, larval behavior seems to limit broad generalizations on the regulation of settlement by larval supply. Knowledge of the relationship is further hindered by the lack of a well founded theoretical relationship between the two variables. The larval supply- settlement transition may have strong general consequences for population connectivity, since larval supply is a result of larval transport, and settlement constrains recruitment. Thus, measuring larval supply and settlement effectively allows more accurate quantification and understanding of larval transport, recruitment and population connectivity.JP would like to thank WHOI Ocean Life Institute for partial funding. FP’s contribution is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation

The Asian decapod Hemigrapsus penicillatus (de Haan, 1835) (Grapsidae, Decapoda) introduced in European waters: status quo and future perspectives

The Asian decapod Hemigrapsus penicillatus (de Haan, 1835) was first recorded in European waters in 1994. The first specimens were collected in the estuary of Charente Maritime on the west coast of France close to La Rochelle. The current range in Europe covers Spanish shallow water habitats of the Bay of Biscay to areas north of La Rochelle (France). Densities of up to 20 specimens per square metre occur. This species has a high temperature and salinity tolerace and will expand its distribution in European waters. It is not clear whether this crab was introduced by shipping in ballast water or as a fouling organism. Based on a study of ship hull fouling in German dry docks this account provides evidence that hull fouling is a likely vector for the introduction of this crab. In August 1993, six juvenile specimens of H. penicillatus were removed from the hull of a car-carrier. After its journey from Japan into European waters this vessel docked in the port of Bremerhaven (Germany) for a routine inspection and coating with antifouling paint

Atlantic Salmon in the Sea

The main facts about the life history of Atlantic salmon have been known for a surprisingly long time. Neill (1946) gives an account of early writings on this subject which makes it clear that, for over four hundred years, it has been known that salmon breed in fresh-water, that they spend a period there before migrating to the sea and that, once in the sea, they undertake long migrations. These earlier writers tended to underestimate the period of time spent in the sea (e.g. they thought it likely that salmon returned to fresh water in the same year that they migrated to sea) but, otherwise, their knowledge of the life history of salmon was remarkably complete and accurate.</jats:p

Memoirs: Baccalaureus maldivensis, a new species of Ascothoracican

1. A new species of the Ascothoracican genus, Bacca-laureus is described. It is distinguished by the possession of lateral processes which contain branches of the gut and of the gonads. 2. The orientation of the segmented body within the mantle is described, and a detailed description of the segmented body is given. 3. A description of the structure and method of attachment of the mantle is given, and of the structure of the lateral coils. 4. The nauplius larva, found within the lumen of the coils, is described. There is a possible further larval stage in some of the larger parasites. 5. The systematic position of the parasite, and the general relationships of the genus Baccalaureus are discussed.</jats:p

Methods of Identification of the Larvae of <i>Balanus Balanoides</i> (L.), <i>B. Crenatus</i> Brug. And <i>Verruca Stroemia</i> O. F. Müller

A description is given of characters which allow the larval stages of Balanus balanoides, B. crenatus and Verruca stroemia to be identified rapidly.It is emphasized that the characters used in this method of identification are only valid for these three species inter se, further work on similar lines for other species may reveal difficulties not apparent in the present scheme.</jats:p