Marine Reserve Design: Optimal Size, Habitats, Species Affinities, Diversity, And Ocean Microclimate

Abstract

The design of marine reserves is complex and fraught with uncertainty. However, protection of critical habitat is of paramount importance for reserve design. We present a case study as an example of a reserve design based on fine-scale habitats, the affinities of exploited species to these habitats, adult mobility, and the physical forcing affecting the dynamics of the habitats. These factors and their interaction are integrated in an algorithm that determines the optimal size and location of a marine reserve for a set of 20 exploited species within five different habitats inside a large kelp forest in southern California. The result is a reserve that encompasses approximately 42% of the kelp forest. Our approach differs fundamentally from many other marine reserve siting methods in which goals of area, diversity, or biomass are targeted a priori. Rather, our method was developed to determine how large a reserve must be within a specific area to protect a self-sustaining assemblage of exploited species. The algorithm is applicable across different ecosystems, spatial scales, and for any number of species. The result is a reserve in which habitat value is optimized for a predetermined set of exploited species against the area left open to exploitation. The importance of fine-scale habitat definitions for the exploited species off La Jolla is exemplified by the spatial pattern of habitats and the stability of these habitats within the kelp forest, both of which appear to be determined by ocean microclimate.

The response of giant kelp (Macrocystis pyrifera) in southern California to low‐frequency climate forcing

“…Comparisons of historical sea urchin abundances off Pt. Loma and La Jolla, the largest forests in California indicate that prior to the regime shift, red (Strongylocentrotus franciscanus), purple (S. purpuratus), and white (Lytechinus anamesus) sea urchins were more abundant (Parnell et al 2006) and the effects of sea urchin grazing on kelp recovery were greater (Tegner and Dayton 1991). Further, the size or stipe numbers of giant kelp after the regime shift appears truncated.…”

Context‐dependent Effects of Fishing: Variation in Trophic Cascades Across Environmental Gradients

“…Subsequently, the indirect effects of predators are expected to be more subtle in highly productive environments. While these patterns suggest that regional scale oceanographic conditions can influence the likelihood of trophic cascades, oceanographic conditions can also vary considerably over much smaller spatial scales and influence the dynamics of kelp forests (Parnell et al 2006).…”

Habitat- and sex-specific life history patterns of yellow tang Zebrasoma flavescens in Hawaii, USA

“…Most studies on ontogenetic variation of habitat use have compared size distributions between habitats (Gillanders et al 2003), and therefore have not considered age structure, sex-specific habitat use patterns or the duration of the lifespan spent in each habitat. When available, information about age-based habitat use can improve conservation planning and design of MPAs (Mumby 2006, Parnell et al 2006) and lead to an understanding of how the amount of available juvenile and adult habitat may influence population size -a potential key to conservation and area-based fisheries management (Halpern et al 2005).…”

“…Most studies on ontogenetic variation of habitat use have compared size distributions between habitats (Gillanders et al 2003), and therefore have not considered age structure, sex-specific habitat use patterns or the duration of the lifespan spent in each habitat. When available, information about age-based habitat use can improve conservation planning and design of MPAs (Mumby 2006, Parnell et al 2006) and lead to an understanding of how the amount of available juvenile and adult habitat may influence population size -a potential key to conservation and area-based fisheries management (Halpern et al 2005).Many species of coral reef fish, including several species of surgeonfish, make ontogenetic shifts in habitat use-an important factor in the organization of fish communities (Robertson 1988, Lawson et al 1999, Lecchini & Galzin 2005, Robertson et al 2005, Pratchett et al 2008. Yellow tang in West Hawaii settle primarily into middepth (10 to 25 m) reef habitat with a high percentage of coral cover (hereafter deeper coral-rich habitat).…”