Effect of Larval Swimming Duration on Success of Metamorphosis and Size of the Ancestrular Lophophore in \u3cem\u3eBugula neritina\u3c/em\u3e (Bryozoa)

There is a growing realization that events during one portion of an organism\u27s life cycle can have both subtle and dramatic effects on other stages in the life history. Lethal and sublethal effects associated with the duration of larval swimming in marine invertebrates were examined for the bryozoan Bugula neritina. Larvae were kept swimming up to a maximum of 28 h at 20{deg}C by exposure to continuous bright fluorescent illumination. At 4-h intervals, samples of 20-40 larvae were removed from bright illumination and were exposed to seawater containing 10 mM excess KCI, an inducer of metamorphosis in this species. Over the first 12 h of larval swimming, an average of about 90% of the larvae initiated and completed metamorphosis; at 16 h, the percentage of larvae initiating and completing metamorphosis dropped significantly. By 28 h, about half of the larvae were initiating metamorphosis, whereas only one-fifth were completing metamorphosis. Larval swimming duration also significantly affected the duration of metamorphosis. By 30 h of larval swimming, individuals were taking about 25% longer to complete metamorphosis. Compared to ancestrulae that developed from larvae that were induced to metamorphose shortly after the onset of swimming, those that swam for greater than 8 h had significantly smaller lophophores. For example, by 28 h of larval swimming the ancestrular lophophore decreased in height, surface area, and volume by about 25%, 40% and 55%, respectively. This marked decrease in lophophore size may ultimately affect the ability of juveniles to sequester food, compete for space, and attain reproductive maturity. Thus, increasing the duration of larval swimming affects both metamorphosis and the development of postlarval structures, which may ultimately influence colony fitness

Ontogenies of Phototactic Behavior and Metamorphic Competence in Larvae of Three Species of \u3cem\u3eBugula\u3c/em\u3e (Bryozoa)

The free swimming larvae of many marine invertebrates actively respond to light. Light cues can be used to regulate position in the water column and to facilitate encountering sites suitable for metamorphosis. We examined the ontogeny of larval phototaxis and the ontogeny of metamorphic competency in larvae from three congeneric species of bryozoans. Larvae of Bugula neritina are positively phototactic on emergence from the brood chamber, whereas larvae of B. simplex and B. stolonifera appear initially photoneutral when populations of larvae are examined. Larvae of all three species become photonegative with time. Temporally coincident with this change to negative phototaxis is an increase in the competency of larvae to initiate metamorphosis. This observation suggests that these events are either physiologically linked or co-occurring, but independent developmental processes. We tested these hypotheses by artificially changing the sign of phototaxis from positive to negative using 10-5 M bath- applied 5-hydroxytryptamine (5HT) in larvae of B. neritina that were swimming for 1 h. Larvae that were photopositive and 1-h-old did not metamorphose at levels significantly different from larvae that were 1-h-old and treated with 5HT (i.e., young, photonegative larvae). Additionally, photopositive larvae which were swimming for 4 h initiated metamorphosis at rates nearly identical to photonegative larvae of the same age. Our data document that in larvae of B. neritina the changes in sign of phototaxis and levels of metamorphic competency are independent developmental events that occur in temporal coincidence. The concurrent timing of these two pathways may have been synchronized through selective processes resulting in a tight coupling between arrival at potentially suitable sites for metamorphosis and ability to respond to metamorphic cues

Utilizing Fishermen Knowledge and Expertise: Keys to Success for Collaborative Fisheries Research

Collaborative fisheries research provides a mechanism for integrating the unique knowledge, experience, and skills of fishermen and scientists. It is a joint intellectual endeavor that begins with the inception of a project and continues until its final stages, with each group having mutual investment in-and ownership of-the project. Collaborative fisheries research promotes communication and trust among fishermen, scientists, and managers and can provide much-needed scientifically valid data for fisheries management. It can enhance federal and state management data collection programs, which span broad sections of coastline, by increasing the ability to detect changes in local metapopulations that may be over-fished or underutilized. We describe a methodology for conducting collaborative fisheries surveys and apply it to marine protected areas along the central California coast. During a series of workshops in 2006, attended by members of the fishing, academic, environmental, and management communities, protocols were established for conducting hook-and-line surveys collaboratively with commercial passenger fishing vessel captains and volunteer recreational anglers. The protocols have been implemented annually since 2007. This case study highlights the effectiveness of-and the essential steps in-developing our collaborative fisheries research and monitoring projects

External fishing effort regulates positive effects of no-take marine protected areas

Marine protected areas (MPAs) have been established across the globe to mitigate the effects of multiple stressors on marine communities. In many locations, MPAs have generated positive effects on fish communities, but the impacts of fishing pressure—the primary stressor MPAs seek to manage—have not been well investigated. We examined changes in fish biomass inside and outside of no-take MPAs over 14 years in central California, USA. Using data from the community-based science program, the California Collaborative Fisheries Research Program, we tested which environmental and human-induced stressors most influence the strength of MPA responses. While temperature and productivity were included in the best fit model, we found that fine-scale fishing effort data, following reserve implementation, best explained the spatial variation in fish community responses to MPAs. Specifically, differences in fish biomass between MPAs and sites open to fishing were larger for reserves near heavily fished locations and these areas exhibited the highest rate of change in fish biomass, indicating strong positive effects of the MPA on the most heavily exploited fish communities. As MPAs continue to be used as a prominent conservation strategy in coastal systems, managers should consider both the suite of human-induced (socio-ecological interactions) and environmental conditions that may alter MPA success as well as establish long-term monitoring programs to fully assess the functionality of marine reserves into the future

Marine protected areas, marine heatwaves, and the resilience of nearshore fish communities

Anthropogenic stressors from climate change can affect individual species, community structure, and ecosystem function. Marine heatwaves (MHWs) are intense thermal anomalies where water temperature is significantly elevated for five or more days. Climate projections suggest an increase in the frequency and severity of MHWs in the coming decades. While there is evidence that marine protected areas (MPAs) may be able to buffer individual species from climate impacts, there is not sufficient evidence to support the idea that MPAs can mitigate large-scale changes in marine communities in response to MHWs. California experienced an intense MHW and subsequent El Niño Southern Oscillation event from 2014 to 2016. We sought to examine changes in rocky reef fish communities at four MPAs and associated reference sites in relation to the MHW. We observed a decline in taxonomic diversity and a profound shift in trophic diversity inside and outside MPAs following the MHW. However, MPAs seemed to dampen the loss of trophic diversity and in the four years following the MHW, taxonomic diversity recovered 75% faster in the MPAs compared to reference sites. Our results suggest that MPAs may contribute to long-term resilience of nearshore fish communities through both resistance to change and recovery from warming events

Managing Bay and Estuarine Ecosystems for Multiple Services

Abstract Managers are moving from a model of managing individual sectors, human activities, or ecosystem services to an ecosystem-based management (EBM) approach which attempts to balance the range of services provided by ecosystems. Applying EBM is often difficult due to inherent tradeoffs in managing for different services. This challenge particularly holds for estuarine systems, which have been heavily altered in most regions and are often subject to intense management interventions. Estuarine managers can often choose among a range of management tactics to enhance a particular service; although some management actions will result in strong tradeoffs, others may enhance multiple services simultaneously. Management of estuarine ecosystems could be improved by distinguishing between optimal management actions for enhancing multiple services and those that have severe tradeoffs. This requires a framework that evaluates tradeoff scenarios and identifies management actions likely to benefit multiple services. We created a management action-services matrix as a first step towards assessing tradeoffs and providing managers with a DOI 10.1007/s12237-013-9602-7 decision support tool. We found that management actions that restored or enhanced natural vegetation (e.g., salt marsh and mangroves) and some shellfish (particularly oysters and oyster reef habitat) benefited multiple services. In contrast, management actions such as desalination, salt pond creation, sand mining, and large container shipping had large net negative effects on several of the other services considered in the matrix. Our framework provides resource managers a simple way to inform EBM decisions and can also be used as a first step in more sophisticated approaches that model service delivery

Variation in Responses of Fishes across Multiple Reserves within a Network of Marine Protected Areas in Temperate Waters

Meta-analyses of field studies have shown that biomass, density, species richness, and size of organisms protected by no-take marine reserves generally increase over time. The magnitude and timing of changes in these response variables, however, vary greatly and depend upon the taxonomic groups protected, size and type of reserve, oceanographic regime, and time since the reserve was implemented. We conducted collaborative, fishery-independent surveys of fishes for seven years in and near newly created marine protected areas (MPAs) in central California, USA. Results showed that initially most MPAs contained more and larger fishes than associated reference sites, likely due to differences in habitat quality. The differences between MPAs and reference sites did not greatly change over the seven years of our study, indicating that reserve benefits will be slow to accumulate in California's temperate eastern boundary current. Fishes in an older reserve that has been closed to fishing since 1973, however, were significantly more abundant and larger than those in associated reference sites. This indicates that reserve benefits are likely to accrue in the California Current ecosystem, but that 20 years or more may be needed to detect significant changes in response variables that are due to MPA implementation. Because of the high spatial and temporal variability of fish recruitment patterns, long-term monitoring is needed to identify positive responses of fishes to protection in the diverse set of habitats in a dynamic eastern boundary current. Qualitative estimates of response variables, such as would be obtained from an expert opinion process, are unlikely to provide an accurate description of MPA performance. Similarly, using one species or one MPA as an indicator is unlikely to provide sufficient resolution to accurately describe the performance of multiple MPAs

Collaborative fisheries research reveals reserve size and age determine efficacy across a network of marine protected areas

A variety of criteria may influence the efficacy of networks of marine protected areas (MPA) designed to enhance biodiversity conservation and provide fisheries benefits. Meta-analyses have evaluated the influence of MPA attributes on abundance, biomass, and size structure of harvested species, reporting that MPA size, age, depth, and connectivity influence the strength of MPA responses. However, few empirical MPA evaluation studies have used consistent sampling methodology across multiple MPAs and years. Our collaborative fisheries research program systematically sampled 12 no-take or highly protective limited-take MPAs and paired fished reference areas across a network spanning 1100 km of coastline to evaluate the factors driving MPA efficacy across a large geographic region. We found that increased size and age consistently contributed to increased fish catch, biomass, and positive species responses inside MPAs, while accounting for factors such as latitude, primary productivity, and distance to the nearest MPA. Our study provides a model framework to collaboratively engage diverse stakeholders in fisheries research and provide high-quality data to assess the success of conservation strategies