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Density dependence in marine protected populations: a review
- J.L. SÁNCHEZ LIZASO, R. GOÑI, O. REÑONES, J.A. GARCÍA CHARTON, R. GALZIN, J.T. BAYLE, P. SÁNCHEZ JEREZ, A. PÉREZ RUZAFA, A.A. RAMOS
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- Journal:
- Environmental Conservation / Volume 27 / Issue 2 / June 2000
- Published online by Cambridge University Press:
- 10 May 2002, pp. 144-158
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The cessation or reduction of fishing in marine protected areas (MPAs) should promote an increase in abundance and mean size and age of previously exploited populations. Thus density-dependent changes in life-history characteristics should occur when populations are allowed to recover in MPAs. In this review, we synthesize the existing information on resource limitation in marine ecosystems, density-dependent changes in life-history traits of exploited populations and evidence for biomass export from MPAs. Most evidence for compensatory changes in biological variables has been derived from observations on populations depleted by high fishing mortality or on strong year classes, but these changes are more evident in juveniles than in adults and in freshwater rather than in marine systems. It is unclear if adults of exploited marine populations are resource limited. This may suggest that exploited populations are controlled mainly by density-independent processes, which could be a consequence of the depleted state of most exploited populations. MPAs could be a useful tool for testing these hypotheses. If we assume that resources become limiting inside MPAs, it is plausible that, if suitable habitats exist, mobile species will search for resources outside of the MPAs, leading to export of biomass to areas which are fished. However, it is not possible to establish from the available data whether this export will be a response to resource limitation inside the MPAs, the result of random movements across MPA boundaries or both. We discuss the implications of this process for the use of MPAs as fisheries management tools.
Effects of marine protected areas on recruitment processes with special reference to Mediterranean littoral ecosystems
- S. PLANES, R. GALZIN, A. GARCIA RUBIES, R. GOÑI, J.-G. HARMELIN, L. LE DIRÉACH, P. LENFANT, A. QUETGLAS
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- Journal:
- Environmental Conservation / Volume 27 / Issue 2 / June 2000
- Published online by Cambridge University Press:
- 10 May 2002, pp. 126-143
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Although site-attached fish can be expected to increase in abundance in marine protected areas (MPAs), there is little known about recruitment effects. The present work reviews concepts and field evidence for enhancement of recruitment of species in MPAs, focusing geographically on the Mediterranean littoral because of its long history of intensive fishery exploitation, but drawing on evidence from studies on recruitment processes in general on MPAs both in the Mediterranean and elsewhere. We considered recruitment as the process of a fish being added to the local population. The general questions of interest are whether the increase in biomass of species protected in MPAs has an effect on recruitment in the MPAs or in neighbouring areas, and, on competition and predation effects on new recruits. A flow diagram of the effects of MPA status on recruitment is developed and employed to identify the relevant processes. The diagram incorporates three levels of factors: (1) characteristics of MPAs (location, size, habitat type, oceanography and level of protection); (2) life stages of species protected in MPAs relevant to recruitment (eggs, larvae, settlers and juveniles); and (3) fundamental processes of dispersal/movement, predation and competition. From this conceptual diagram, the following main components of the recruitment process were identified and used to structure the review: (1) relationship between the ecology of pelagic stages and the design, location and oceanographic regime of MPAs; (2) effects of protection in MPAs from fishery exploitation of nursery habitats on settlement success; and (3) effects of protection on survival of settlers and juveniles from competition and predation. We found an exceptionally low number of studies specifically addressing recruitment processes in MPAs. This was particularly the case in what concerns the relationship between larval ecology and the characteristics and oceanographic regime of MPAs. The effectiveness of MPAs in promoting recruitment mainly depends on the locations and on sizes of the MPAs in relation to the reproductive biology and larval ecology of the species concerned. The locations and sizes of MPAs in turn depend on MPA objectives, whether the purpose is to protect entire life cycles, the juveniles, or to increase egg production and larval export. The assessment of the relationship between the protection of nursery habitats and settlement success indicates that the magnitude of the effects of protection depends on whether the recruitment of the species involved is restricted to a narrowly-defined set of environmental conditions or, on the contrary, can occur in diverse environments, including areas beyond the influence of the MPAs. Thus, the locations of MPAs determine the habitats which are protected and, consequently, the species, the settlement of which will be favoured. For Mediterranean shallow-water species, the near-shore zone encompasses most of the essential nursery habitats for protection. Recruitment studies conducted in MPAs in the north-western Mediterranean have showed no differences in survival of newly-settled littoral fish between MPAs and the areas outside of them. Conversely, for older recruits, mortality was found to be higher inside MPAs, probably due to the increased abundance and size of large predators. This study highlights the almost total absence of studies addressing even the most elementary questions of recruitment in the specific context of MPAs.
Spatio-temporal variability in growth of juvenile sparid fishes from the Mediterranean littoral zone
- S. Planes, E. Macpherson, F. Biagi, A. Garcia-Rubies, J. Harmelin, M. Harmelin-Vivien, J.-Y. Jouvenel, L. Tunesi, L. Vigliola, R. Galzin
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- Journal:
- Journal of the Marine Biological Association of the United Kingdom / Volume 79 / Issue 1 / February 1999
- Published online by Cambridge University Press:
- 04 April 2001, pp. 137-143
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Populations of three species of juvenile Sparidae (Diplodus puntazzo, Diplodus sargus and Diplodus vulgaris) were sampled at different spatial scales in the north-western Mediterranean Sea over two years to follow growth after settlement. Length–frequency distributions were collected each week for periods of six months following the arrival of off-shore larvae in inshore habitats. Data were collected by underwater visual census along permanent transects.
Growth rate measured as the slope of the linear relationship between mean size and time varied between species. Diplodus puntazzo (0.160 mm d−1) and D. vulgaris (0.202 mm d−1), which are settling in winter experienced slower growth than D. sargus (0.567 mm d−1) which settles in summer. It is concluded that the difference was in part due to water temperature. Analysis of growth rate within each species also revealed significant differences among sites probably related to the currents and the water mass temperatures.
Endoparasite species richness of New Caledonian butterfly fishes: host density and diet matter
- S. MORAND, T. H. CRIBB, M. KULBICKI, M. C. RIGBY, C. CHAUVET, V. DUFOUR, E. FALIEX, R. GALZIN, C. M. LO, A. LO-YAT, S. PICHELIN, P. SASAL
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- Journal:
- Parasitology / Volume 121 / Issue 1 / July 2000
- Published online by Cambridge University Press:
- 01 July 2000, pp. 65-73
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Ecological factors may influence the number of parasites encountered and, thus, parasite species richness. These factors include diet, gregarity, conspecific and total host density, habitat, body size, vagility, and migration. One means of examining the influence of these factors on parasite species richness is through a comparative analysis of the parasites of different, but related, host species. In contrast to most comparative studies of parasite species richness of fish, which have been conducted by using data from the literature, the present study uses data obtained by the investigators. Coral reef fishes vary widely in the above ecological factors and are frequently parasitized by a diverse array of parasites. We, therefore, chose to investigate how the above ecological factors influence parasite species richness in coral reef fishes. We investigated the endoparasite species richness of 21 species of butterfly fishes (Chaetodontidae) of New Caledonia. We mapped the diet characters on the existing butterfly fish phylogeny and found that omnivory appears to be ancestral. We also mapped the estimated endoparasite species richness, coded from low to high parasite species richness, on the existing butterfly fish phylogeny and found that low parasite species richness appears to be associated with the ancestral state of omnivory. Different dietary and social strategies appear to have evolved more than once, with the exception of obligate coralivory, which appears to have evolved only once. Finally, after controlling for phylogenetic relationships, we found that only the percentage of plankton in the diet and conspecific host density were positively correlated with endoparasite species richness.