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Ecological influences on reproduction in sea urchins, particularly photoperiod, have been studied extensively. Effects of proximate environmental factors (temperature, water motion, food) on reproduction of purple urchins, Strongylocentrotus purpuratus (Stimpson, 1857), were sampled monthly for 2 yrs for intertidal, and subtidal populations at the same latitude in the Point Loma kelp forest, San Diego, California, USA. Gonad index (GI) was highest at 8 m, intermediate in the intertidal, and lowest at 18 m. GI increased across sites from spring through autumn and decreased sharply from late autumn through early winter. Stomach index (SI) peaked in summer and in autumn-winter. Increases in SI followed temporal peaks in drift plant abundance, but preceded increases in GI. Temperatures ranged from 11-22 degrees C, varying inversely with depth. Water movements were highest at deeper sites. Spawning coincided with high wave periods. Abundance of drift macroalgal food generally increased from deep to shallow sites, with rare peaks in abundance of intertidal drift. Algal food quantity appears to regulate reproductive output, not timing. ON ratio of drift kelp was generally higher, and nitrogen correspondingly lower, at warmer temperatures or shallower depths; nitrogen was lower in drift than in live kelp. Gonadal growth, development, and spawning occurred earlier at deeper subtidal sites with faster flows, lower temperatures, and higher food quality, despite low drift abundance. Gonad production was highest intertidally despite high population density, prolonged high temperatures > 17 degrees C limiting gametogenesis, and only sporadic availability of drift. Naturally co-occurring abiotic and biotic factors combine to affect reproduction in S. purpuratus.

Traditional fisheries management in southern California has failed, in part because it is based on an assumption of an unvarying environment and is focused on size limits rather than insuring the persistence of aggregations of large fecund individuals. The combined effect of low frequency climatic variability and anthropogenic perturbations can have dramatic consequences for abalone in southern California. Abalone species are tightly linked to kelp forest ecosystems that, besides furnishing habitat, also provide the main food source for abalone. In southern California, kelp canopies are very sensitive to oceanographic climate because the kelp depend upon high nutrients in the water column. Oceanic warming, in turn, results in decreased nutrients in the surface water, and this is correlated with marked reductions in giant kelp biomass.Here we address the additive effects of ocean warming on two species of California abalone (the red abalone, Haliotis rufescens; and the green abalone, H. fulgens) by subjecting them to varied environmental conditions similar to cool, normal, and warm phases of the California current in the southern California Bight. Our experimental design simultaneously tested the synergistic effects of temperature and food quantity and quality on survivorship, growth, and reproduction. For red abalone, warm temperatures increased the onset of withering syndrome, a fatal abalone disease, and halted growth and reproduction. In contrast, green abalone survivorship, growth, and reproduction were relatively robust irrespective of temperature, while their growth and reproduction were most strongly influenced by food quantity. We found clear evidence suggesting that, combined with overfishing, California abalone populations are adversely affected by ecosystem responses to ocean warming: Cool‐water red abalone suffer stronger consequences in warm water than do green abalone. Conservation, restoration, and recovery plans of remnant California abalone populations must consider these relationships when taking any action.

We developed an individual-based, spatially explicit population-dynamics model to explore the effects of temperature, fishing pressure, and reserve size on red abalone (Haliotis rufescens) populations at two of the northern Channel Islands off the coast of California. The model locations represent the “warm” Santa Cruz Island, which has a fishing history of declining abalone stocks, and the “cold” San Miguel Island, which has a history of stable catches. We investigated the effects of three temperature scenarios for 100-year periods on the behavior of each population. In the first scenario we used the real temperature environment (sea surface temperature, SST) from the last 100 years; results showed a decline in both model populations over the last 20 years, with and without fishing. In the second scenario model runs using an SST time series generated from current conditions at the islands showed that in the absence of larval connectivity the warm population would go extinct within 75 years regardless of fishing level. The final SST scenario involved a range of constant, potential SSTs that could occur in the future; abalone populations persisted when the SST was between 11 ̊C and 16 ̊C. The influence of temperature on the model populations and the latitudinal range of suitable SST suggest a northward migration of the real red abalone range as SST increases over the next 100 years. Efforts to rebuild or protect populations for the future should consider which West Coast regions would provide suitable red abalone habitat given rising ocean temperatures. INTRODUCTION Abalone are long-lived, broadcast-spawning coastal gastropods that live in relatively predictable and accessible locations (reviewed by Tegner 1989). They are a valuable fishery resource, yet overexploitation has been a problem in every producing country in the world (e.g., Breen 1986; Tegner 1989). California once supported fisheries for five species of abalones, but all commercial harvesting was halted in 1997 (Tegner 2000). One of these over-exploited species, white abalone (Haliotis sorenseni), recently became the first marine invertebrate in the United States to be listed as an endangered species under the federal Endangered Species Act (Hobday et al. 2001). Recovery efforts for this and other abalone species are underway in California. Abalone fisheries have typically been managed by regulating a minimum size for capture, although quotas now exist in regions where harvesting continues (e.g., Tasmania, South Africa, New Zealand). The size-limit approach was intended to allow several years of reproduction before capture was possible. This approach may succeed if recruitment is frequent, but the combination of abalone life-history characters—specifically, long life span and broadcast spawning—indicate that high recruitment does not occur every year (Hobday et al. 2001). Successful reproduction in broadcast spawning invertebrates also depends on proximity between spawning individuals and their gametes (e.g., Pennington 1985; Babcock and Keesing 1998; Levitan 1998; Claereboudt 1999). Intense fishing can increase the distance between neighbors such that fertilization cannot occur, leading to recruitment failure (e.g., Shepherd and Brown 1993; Hughes and Tanner 1998). Recruitment failure over a period of time is likely to lead to dramatic population decline and loss of the fishery resource (Shepherd et al. 1998). Fishing has often borne the sole blame for stock collapse in many regions. It is important to note that recruitment failure can occur in the absence of fishing, and some investigators suggest that variation in the environment may be a causative factor in irregular recruitment of abalone (e.g., Shepherd et al. 1998). Indeed, the life history characteristics that allow abalone to persist evolved well before human exploitation began, and so irregular recruitment may be a natural process, offset by long-lived adults. The role of the environment has not been clearly demonstrated in the population dynamics of these marine invertebrates, in part because manipulating and monitoring subtidal populations is difficult. Population models are one tool that may improve our understanding of these complex natural patterns (e.g., Claereboudt 1999). Our goal in this study was to develop a model that incorporated abalone population dynamics, environmental variation, and level of fishing to explore production characteristics of abalone populations. The

Kelp forests are phyletically diverse, structurally complex and highly productive components of coldwater rocky marine coastlines. This paper reviews the conditions in which kelp forests develop globally and where, why and at what rate they become deforested. The ecology and long archaeological history of kelp forests are examined through case studies from southern California, the Aleutian Islands and the western North Atlantic, well-studied locations that represent the widest possible range in kelp forest biodiversity. Global distribution of kelp forests is physiologically constrained by light at high latitudes and by nutrients, warm temperatures and other macrophytes at low latitudes. Within mid-latitude belts (roughly 40–60° latitude in both hemispheres) well-developed kelp forests are most threatened by herbivory, usually from sea urchins. Overfishing and extirpation of highly valued vertebrate apex predators often triggered herbivore population increases, leading to widespread kelp deforestation. Such deforestations have the most profound and lasting impacts on species-depauperate systems, such as those in Alaska and the western North Atlantic. Globally urchin-induced deforestation has been increasing over the past 2–3 decades. Continued fishing down of coastal food webs has resulted in shifting harvesting targets from apex predators to their invertebrate prey, including kelp-grazing herbivores. The recent global expansion of sea urchin harvesting has led to the widespread extirpation of this herbivore, and kelp forests have returned in some locations but, for the first time, these forests are devoid of vertebrate apex predators. In the western North Atlantic, large predatory crabs have recently filled this void and they have become the new apex predator in this system. Similar shifts from fish- to crab-dominance may have occurred in coastal zones of the United Kingdom and Japan, where large predatory finfish were extirpated long ago. Three North American case studies of kelp forests were examined to determine their long history with humans and project the status of future kelp forests to the year 2025. Fishing impacts on kelp forest systems have been both profound and much longer in duration than previously thought. Archaeological data suggest that coastal peoples exploited kelp forest organisms for thousands of years, occasionally resulting in localized losses of apex predators, outbreaks of sea urchin populations and probably small-scale deforestation. Over the past two centuries, commercial exploitation for export led to the extirpation of sea urchin predators, such as the sea otter in the North Pacific and predatory fishes like the cod in the North Atlantic. The large-scale removal of predators for export markets increased sea urchin abundances and promoted the decline of kelp forests over vast areas. Despite southern California having one of the longest known associations with coastal kelp forests, widespread deforestation is rare. It is possible that functional redundancies among predators and herbivores make this most diverse system most stable. Such biodiverse kelp forests may also resist invasion from non-native species. In the species-depauperate western North Atlantic, introduced algal competitors carpet the benthos and threaten future kelp dominance. There, other non-native herbivores and predators have become established and dominant components of this system. Climate changes have had measurable impacts on kelp forest ecosystems and efforts to control the emission of greenhouse gasses should be a global priority. However, overfishing appears to be the greatest manageable threat to kelp forest ecosystems over the 2025 time horizon. Management should focus on minimizing fishing impacts and restoring populations of functionally important species in these systems.

We developed an individual-based, spatially explicit population-dynamics model to explore the effects of temperature, fishing pressure, and reserve size on red abalone (Haliotis rufescens) populations at two of the northern Channel Islands off the coast of California. The model locations represent the "warm" Santa Cruz Island, which has a fishing history of declining abalone stocks, and the "cold" San Miguel Island, which has a history of stable catches. We investigated the effects of three temperature scenarios for 100-year periods on the behavior of each population. In the first scenario we used the real temperature environment (sea surface temperature, SST) from the last 100 years; results showed a decline in both model populations over the last 20 years, with and without fishing. In the second scenario model runs using an SST time series generated from current conditions at the islands showed that in the absence of larval connectivity the warm population would go extinct within 75 years regardless of fishing level. The final SST scenario involved a range of constant, potential SSTs that could occur in the future; abalone populations persisted when the SST was between 11degreesC and 16degreesC.The influence of temperature on the model populations and the latitudinal range of suitable SST suggest a northward migration of the real red abalone range as SST increases over the next 100 years. Efforts to rebuild or protect populations for the future should consider which West Coast regions would provide suitable red abalone habitat given rising ocean temperatures.

The Bulletin of the Ecological Society of AmericaVolume 82, Issue 1 p. 12-14 ArticleFree Access Minutes of the ESA Governing Board Meeting, 19-20 May 2000 First published: 01 January 2001 https://doi.org/10.1890/0012-9623(2001)082[0012:MOTEGB]2.0.CO;2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume82, Issue1January 2001Pages 12-14 RelatedInformation

Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.

Coastal zones are usually managed with two main objectives: (1) conservation/maintenance of biodiversity and. intrinsic ecosystem services and (2) maintenance of sustainable fisheries. The management needs that can be met with marine protected areas fall into corresponding categories. First, fully protected (that is, no-take) reserves-parks-offer benchmarks and protect ecosystem integrity while encouraging research, education, and aesthetic appreciation of nature. Second, by allowing focused local control of human impacts, marine protected areas can be used to focus more intense local management designed to increase yield and allow research to help define sustainability and protect against uncertainty by using carefully managed fisheries as a research tool. We have been gambling with the future by establishing a poor balance between short-term profit and long-term risks. The absence of meaningful, fully protected reserves has produced a situation in which there are virtually no areas north of the Antarctic in the world's oceans that have exploitable resources where scientists can study natural marine systems. In most areas the higher-order predators and many other important species have been virtually eliminated; many benthic habitats have been much changed by fishing activities. Without solid data documenting changes through time, the relative merits of various causes and effects that operate in complex ecological systems can always be argued. Without natural systems important questions cannot be studied-for example, how the ecosystem roles of various species can be assessed, how they can be managed in a sustainable manner, and how we can evaluate resilience or relative rates of recovery. Networks of fully-protected reserves could facilitate research into such questions, contribute to the recovery of many coastal systems, and enable society to enrich its existence by observing species that should be part of its heritage (Murray ct al., 1999). The use of marine protected areas as fishing refugia has met strong resistance by fishers and many managers, and it is misunderstood by many conservation biologists because different proponents have different, usually simplistic, visions. It is important to spell out the objectives of each proposed example. Our essential habitat perspective emphasizes that each situation depends on specific life-history parameters and emphasizes critical thresholds in population dynamics, including density and behavior for fertilization, transport processes, settlement, survivorship, and growth to maturity. These are extremely difficult problems, and we cannot expect simplistic solutions to be effective. The only basis for optimism is that most of the seriously affected species are not yet extinct, and we still have a little time to establish permanent fully protected reserves to allow mankind to appreciate its rich but much depleted biological heritage. At least in some systems recovery can be measured over short time scales (<10 yrs), whereas others are much slower. Society as a whole is the ultimate stakeholder, not only the commercial and sports fishing industries that so dominate the public arena. Society will have to play a more active role if these species and habitats are to be saved.

Outplanting of hatchery-reared juvenile abalone has received much attention as a strategy for enhancement of depleted natural stocks. Most outplants attempted to date appear to have been unsuccessful. However, based on genetic analyses of a population sample taken in 1992, it has recently been suggested that a 1979 outplanting of red abalone Haliotis rufescens, on the south side of San Miguel Island (California, USA), was successful and probably sustained the fishery there through the 1980s. We resampled the San Miguel population in 1999 and found no genetic signature of the outplants. Allelic frequencies in our 1999 sample closely resemble those observed in a pre-outplant 1979 southern California sample and two 1999 northern California populations. All genotypic frequencies were in Hardy-Weinberg expected proportions. We also assessed mtDNA diversity at San Miguel and found it not to differ from that of 2 robust northern California populations of H. rufescens. Our results suggest that either the composition of the San Miguel abalone population changed rapidly between 1992 and 1999, or the genetic anomalies attributed to hatchery source for the 1992 sample were due to sample degradation or other laboratory artifacts. Since we lack samples from the 1992 collections, we cannot directly test which explanation is valid. However, several lines of reasoning call into question the earlier conclusion of outplant success.

Marine invertebrates have long been considered to be resistant to overfishing. However, a growing number of exploited taxa have declined substantially and even disappeared from parts of their former range. We consider the case of the white abalone (Haliotis sorenseni); the first marine invertebrate proposed for the US endangered species list. This high-value species was one of five abalones targeted in the California and Mexico fisheries; it is now rare and protected from fishing. The biological characteristics of this deep-living abalone indicate that it was particularly vulnerable to over-exploitation; reduction of density or group size is now known to lead to declines in fertilization success and recruitment failure. Warning signs of potential problems existed both pre- and post-exploitation but were not recognized. In particular, serial depletion was not detected because catch was not analyzed spatially, perhaps because total landings were reasonably stable for the short period of exploitation. Recent submersible surveys led to estimates that white abalone now number less than 2,600 animals or 0.1% of the estimated pre-exploitation population size. Densities and estimated population sizes are less than 100 animals, at all but one location. Alternate explanations for the decline in abundance were considered and only exploitation-linked factors, such as sub-legal mortality and illegal fishing, were likely contributors. Episodic recruitment appears to be a characteristic of broadcast-spawning, long-lived species and may make them particularly vulnerable to over-exploitation. Management strategies based on size limits that allow a few years of spawning prior to reaching minimum legal size are insufficient. Sustainable fisheries will require multiple protected areas to preserve brood stock aggregations necessary for successful fertilization.

Improved management approaches are needed to reduce the rate at which humans are depleting exploited marine populations and degrading marine ecosystems. Networks of no-take marine reserves are promising management tools because of their potential to (1) protect coastal ecosystem structure and, functioning, (2) benefit exploited populations and fisheries, (3) improve scientific understanding of marine ecosystems, and (4) provide enriched opportunities for non-extractive human activities. By protecting marine ecosystems and their populations, no-take reserve networks can reduce risk by providing important insurance for fishery managers against overexploitation of individual populations. Replicated reserves also foster strong scientific testing of fishery and conservation management strategies. Reserve networks will require social acceptance, adequate enforcement, and effective scientific evaluation to be successful. Processes for reserve establishment should accommodate adaptive management so boundaries and regulations can be modified to enhance performance. However, even well-designed. reserve networks will require continued conservation efforts outside reserve boundaries to be effective. Establishing networks of no-take reserves is a process-oriented, precautionary management strategy that protects functional attributes of marine ecosystems. As an addition to fishery management practices and other conservation efforts, no-take reserve networks may improve the status of exploited populations while conserving marine resources for future generations.

Marine fisheries are in decline worldwide. Increasing problems of bycatch and habitat destruction, and now a growing realization of the role of climate on fished populations, are leading to widespread recognition that the single species approach to fisheries management is not effective. These problems are moving management from its traditional focus on maximizing the yield of individual resources towards broader considerations of direct and indirect impacts of fishing on ecosystems as a whole. Thus, the International Council for the Exploration of the Sea (ICES) and the Scientific Committee for Oceanic Research (SCOR) convened a meeting on the Ecosystem Effects of Fishing this March in Montpellier, France. The objective was to provide a global synthesis of the impacts of fishing on marine ecosystems, to report methods for quantifying ecosystem effects, and to provide a forum for discussion of how objectives relating to the conservation of nature can be integrated into fisheries management. Led by Michael Sinclair (Bedford Institute of Oceanography, Dartmouth, Canada) and Henrik Gislason (University of Copenhagen, Charlottenlund, Denmark), the symposium attracted more than 300 participants from 54 countries * Invited presentations and a selection of papers from the many posters that added to the discussion will be published in the ICES Journal of Marine Science. *Invited presentations and a selection of papers from the many posters that added to the discussion will be published in the ICES Journal of Marine Science..

This paper integrates long-term descriptive and experimental studies of the effects of ocean climate on inter- and intraspecific competition, as expressed by recruitment, density, survivorship, growth, and reproduction of the most conspicuous kelp species in the Point Loma kelp forest community off San Diego, California, USA. The species included Macrocystis pyrifera, with a floating canopy; Pterygophora californica and Eisenia arborea, which rely on stipes to support their canopy; Laminaria farlowii, with a prostrate canopy; and a speciose red algal turf. To evaluate the roles of large-scale oceanographic processes on biological processes across important depth gradients, the study was carried out over nine years during a cold-water, nutrient-rich La Nina event (1988-1989) and a warm-water, nutrient-stressed El Nino period (1992-1994), over a depth range of 8-23 m. This depth range encompassed strong physical gradients involving factors that are critical for kelp growth, including bottom temperatures (correlated with nutrients) and light levels.To examine interactions among these kelps, we established clearings across the depth gradient and then manipulated Macrocystis recruit densities. The demographic responses offer an understanding of the "fundamental" vs. "realized" niches of these species. Evaluating these patterns, as they are influenced by inter- and intraspecific competition, offers insights into the "realized niches" of the kelps. With the exception of some understory effects on Macrocystis recruitment and some evidence of intraspecific competition during the nutrient-rich La Nina conditions, we found little influence of competitive effects on Macrocystis. The response of Pterygophora to manipulations and disturbances suggests light-limited recruitment, and competition with Macrocystis was exhibited via reduced growth and reproduction, but not survivorship. No nutrient stress was observed in Pterygophora reproduction. Eisenia recruitment is rare, but once established, juveniles had very good survivorship, with growth and reproduction reduced by depth; the Macrocystis treatment was more important than depth, suggesting the importance of light to Eisenia recruitment and growth. In general, Macrocystis had massive effects on Laminaria growth and reproduction, the strength varying with depth. In particular, there were very strong effects of competition with Macrocystis during the nutrient-rich La Nina period when Macrocystis had a dense surface canopy. In addition to the Macrocystis effects, there were some significant Pterygophora effects on Laminaria growth during El Nino.The strongest biological definition of realized niches occurred during the nutrient-rich La Nina period, especially in shallow depths. One of the most important conclusions of this paper is the appreciation of the importance of scaling in time to include oceanographic climate. There are many seasonal patterns, but the interannual scales that encompass Er Ninos and La Ninas, and ultimately the interdecadal-scale oceanographic regime shifts that affect the intensity of canopy competition with Macrocystis, are critical for this system because surface-water nutrients have pervasive long-term effects an the other kelps. Small-scale patterns are driven by local processes (competition, disturbance, dispersal, etc.) that potentially are important at larger scales; however, our most lasting effects result from very large-scale, low-frequency episodic changes in nutrients, with cascading competitive consequences to the other algal populations in the community.