Large scale pattern of recruitment by the labrid, Semicossyphus pulcher: Causes and implications

The pattern of recruitment of sheephead, Semicossyphus pulcher, is described throughout a major portion of its range over a period of 7–9 years. The relative recruitment success was determined using both field transects and age-structure data. The observed pattern of recruitment was compared to both spatial and year-to-year variations in the current regime within the region using both average flow data (CalCOFI data base) and satellite imagery. It was found that in areas with larval sources to the north and south, recruitment occurred consistently from year-to-year. However, in areas where there was no larval sources upstream of the typical current direction, recruitment was highly variable and dependent upon anomalous events in the current flow. These anomalous events are considered on two levels: low-level events, which last from days to weeks, thereby affecting recruitment of only one or a few species, and high-level events, which last from months to years (e.g. El Niño events), affecting recruitment of many species. A positive relationship is found between frequency of recruitment events and density of adult populations. In addition, the persistence of populations is dependent upon recruitment frequency and the longevity of the individuals. The interaction between recruitment frequency, population density and persistence is considered to be important in determining the northern distribution limit of sheephead at Point Conception (also a major break for many other species). In the past, this faunal break has typically been attributed to temperature differences and inferred physiological constraints. It is concluded, from the findings in this study, that the faunal break at Point Conception is heavily influenced by hydrographic constraints on dispersal

Toward identification of larval sailfish (Istiophorus platypterus), white marlin (Tetrapturus albidus), and blue marlin (Makaira nigricans) in the western North Atlantic Ocean*

The identification of larval istiophorid billfishes from the western North Atlantic Ocean has long been problematic. In the present study, a molecular technique was used to positively identify 27 larval white marlin (Tetrapturus albidus), 96 larval blue marlin (Makaira nigricans), and 591 larval sailfish (Istiophorus platypterus) from the Straits of Florida and the Bahamas. Nine morphometric measurements were taken for a subset of larvae (species known), and lower jaw pigment patterns were recorded on a grid. Canonical variates analysis (CVA) was used to reveal the extent to which the combination of morphometric, pigment pattern, and month of capture information was diagnostic to species level. Linear regression revealed species-specific relationships between the ratio of snout length to eye orbit diameter and standard length (SL). Confidence limits about these relationships served as defining characters for sailfish >10 mm SL and for blue and white marlin >17 mm SL. Pigment pattern analysis indicated that 40% of the preflexion blue marlin examined possessed a characteristic lower jaw pigment pattern and that 62% of sailfish larvae were identifiable by lower jaw pigments alone. An identification key was constructed based on pigment patterns, month of capture, and relationships between SL and the ratio of snout length to eye orbit diameter. The key yielded identifications for 69.4% of 304 (blind sample) larvae used to test it; only one of these identifications was incorrect. Of the 93 larvae that could not be identified by the key, 71 (76.3%) were correctly identified with CVA. Although identif ication of certain larval specimens may always require molecular techniques, it is encouraging that the majority (92.4%) of istiophorid larvae examined were ultimately identifiable from external characteristics alone

Expatriation of Xyrichtys novacula (Pisces: Labridae) larvae: Evidence of rapid cross-slope exchange

Larvae of Xyrichtys novacula (Pisces: Labridae) have been collected in the Middle Atlantic Bight (MAB) hundreds of kilometers north of reported adult ranges by both the Marine Monitoring and Assessment Program (MARMAP) and by our ichthyoplankton cruises. These larvae could be from a previously unknown population north of Cape Hatteras or they could have been transported north from southern populations. In order to examine these two hypotheses both biological and physical oceanographic data were considered, including size-specific larval distribution, larval age, vertical distribution of larvae, satellite imagery of sea surface temperature, and temperature and salinity measurements. Larvae captured during our 1988 ichthyoplankton cruises ranged from 3.11 mm to 13.13 mm in length with small larvae (≤5 mm) found in association with the shelf break and larger larvae (\u3e5 mm) found distributed across the outer shelf and shelf break. Based on aging of daily otolith increments larval age was found to range from 7 to 36 days and backcalculated birthdates, derived from estimated age and date of capture, were found to be from mid-June to early August. Larvae occurred predominantly near the surface (≤10 m) at night and deeper (\u3e10 m) during the day. Concurrent hydrographic data revealed that small larvae were found in shelf water (\u3c35 psu) but with underlying slope water (\u3e35 psu) at depths of 15–30 m suggesting that small larvae were in shelf water at night but either at the boundary with or within slope water during the day. Satellite imagery from 1988 revealed a warm-core ring offshore of our 1988 sampling area. An analysis of historical warm-core ring data from Northwest Atlantic Fisheries Organization data reports in conjunction with captures of X. novacula during the years 1984–1987 demonstrated that the presence of warm-core rings offshore was associated with the occurrence of X. novacula on the MAB shelf, north of Chesapeake Bay. The feasibility of northward transport associated with the Gulf Stream and cross-slope transport associated with a warm-core ring was examined with a simple model which demonstrated that the required transport velocities were within the range of velocities presented in the literature. It is suggested that larvae are rapidly transported from south of Cape Hatteras to the MAB shelf break by advection associated with the Gulf Stream and a concomitant cross-slope flow related with the western edge of warm-core rings

Movements and spawning of white marlin (Tetrapturus albidus) and blue marlin (Makaira nigricans) off Punta Cana, Dominican Republic

With a focus on white marlin (Tetrapturus albidus), a concurrent electronic tagging and larval sampling effort was conducted in the vicinity of Mona Passage (off southeast Hispaniola), Dominican Republic, during April and May 2003. Objectives were 1) to characterize the horizontal and vertical movement of adults captured from the area by using pop-up satellite archival tags (PSATs); and 2) by means of larval sampling, to investigate whether fish were reproducing. Trolling from a sportfishing vessel yielded eight adult white marlin and one blue marlin (Makaira nigricans); PSAT tags were deployed on all but one of these individuals. The exception was a female white marlin that was unsuitable for tagging because of injury; the reproductive state of its ovaries was examined histologically. Seven of the PSATs reported data summaries for water depth, temperature, and light levels measured every minute for periods ranging from 28 to 40 days. Displacement of marlin from the location of release to the point of tag pop-up ranged from 3l.6 to 267.7 nautical miles (nmi) and a mean displacement was 3.4 nmi per day for white marlin. White and blue marlin mean daily displacements appeared constrained compared to the results of other marlin PSAT tagging studies. White marlin ovarian sections contained postovulatory follicles and final maturation-stage oocytes, which indicated recent and imminent spawning. Neuston tows (n=23) yielded 18 istiophorid larvae: eight were white marlin, four were blue marlin, and six could not be identified to species. We speculate that the constrained movement patterns of adults may be linked to reproductive activity for both marlin species, and, if true, these movement patterns may have several implications for management. Protection of the potentially important white marlin spawning ground near Mona Passage seems warranted, at least until further studies can be conducted on the temporal and spatial extent of reproduction and associated adult movement

The Role of Long Distance Dispersal Versus Local Retention in Replenishing Marine Populations

Early models and evidence from genetics suggested that long distance dispersal of larvae is likely a common event leading to considerable population connectivity among distant populations. However, recent evidence strongly suggests that local retention is more the rule, and that long distance transport is likely insufficient to sustain marine populations over demographic timescales. We build on earlier model results to examine the probability of larval dispersal to downstream islands within different regions of the Caribbean at varying distances from source populations. Through repeated runs of an ocean circulation model (MICOM), coupled with a random flight model estimating larval sub-grid turbulent motion, we estimate the likelihood of particular circulation events transporting large numbers of larvae to within 9km radii of downstream populations, as well as account for total accumulations of larvae over each year. Further, we incorporate realistic larval behavior and mortality estimates and production variability into our models. Our results are consistent with the hypothesis that marine populations must rely on mechanisms enhancing self-recruitment rather than depend on distant ‘source’ populations

Population connectivity in marine systems : an overview

Author Posting. © Oceanography Society, 2007. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 20, 3 (2007): 14-21.There is growing consensus that life within the world’s ocean is under considerable and increasing stress from human activities (Hutchings, 2000; Jackson et al., 2001). This unprecedented strain on both the structure and function of marine ecosystems has led to calls for new management approaches to counter anthropogenic impacts in the coastal ocean (Botsford et al., 1997; Browman and Stergiou, 2004: Pikitch et al., 2004). Spatial management, including Marine Protected Areas (MPAs), has been touted as a method for both conserving biodiversity and managing fisheries (Agardy, 1997). Continuing debates on the efficacy of MPAs have identified the need for models that capture the spatial dynamics of marine populations, especially with respect to larval dispersal (Willis et al., 2003; Sale et al., 2005). Theoretical studies suggest that population connectivity plays a fundamental role in local and metapopulation dynamics, community dynamics and structure, genetic diversity, and the resiliency of populations to human exploitation (Hastings and Harrison, 1994; Botsford et al., 2001). Modeling efforts have been hindered, however, by the paucity of empirical estimates of, and knowledge of the processes controlling, population connectivity in ocean ecosystems. While progress has been made with older life stages, the larval-dispersal component of connectivity remains unresolved for most marine populations. This lack of knowledge represents a fundamental obstacle to obtaining a comprehensive understanding of the population dynamics of marine organisms. Furthermore, a lack of spatial context that such information would provide has limited the ability of ecologists to evaluate the design and potential benefits of novel conservation and resource-management strategies.Over the years, we have each received support from a variety of agencies in support of research relevant to Population Connectivity; in addition to NSF, we acknowledge funding from the World Bank/GEF Coral Reef Targeted Research Program, University of Miami’s Maytag Chair in Ichthyology, the Oak Foundation, and the Woods Hole Oceanographic Institutio

Behavior Constrains the Dispersal of Long-Lived Spiny Lobster Larvae

Behavior such as ontogenetic vertical migration (OVM) limits the transport of marine larvae with short pelagic larval durations (PLDs), but its effect on the supposed long-distance dispersal of larvae with long PLDs is unknown. We conducted laboratory tests of ontogenetic change in larval phototaxis and examined size-specific patterns of larval distribution in the plankton to characterize OVM in the Caribbean spiny lobster Panulirus argus during its long (6 mo) PLD. We then used a coupled biophysical model to explore the consequences of OVM and hydrodynamics on larval P. argus dispersal in the Caribbean Sea. Larvae reared in the laboratory were positively phototatic for the first 2 mo and then avoided light thereafter, similar that seen in the planktonic distribution of same-sized larvae. Simulations of larval dispersal from 13 spawning sites in the Caribbean Sea predicted that twice as many larvae would recruit to nurseries if they displayed OVM compared with passive dispersers. Larvae with OVM typically settled spawned, while passive dispersers often settled \u3e1000 km away. OVM also produced an asymmetrical bimodal pattern of dispersal dominated by larvae that settled near their origin (similar to 60%), but showed a second peak of larvae that dispersed over long distances (similar to 20%). Hydrodynamics created subregional differences in the potential for self-recruitment. Our findings suggest that (1) larval behavior constrains the dispersal of even long-lived larvae, particularly in tandem with retentive oceanographic environments, and (2) larval sources of P. argus in the Caribbean Sea cannot be estimated from passive transport and surface circulation

The Influence of a Ubiquitous Filter Feeder on Coastal Microbial Communities.

Doliolids have a unique ability to impact the marine microbial community through bloom events and high filtration rates. Their predation on large eukaryotic microorganisms is established and evidence of predation on smaller prokaryotic microorganisms is beginning to emerge. We studied the retention of both eukaryotic and prokaryotic microbial taxa by wild-caught doliolids in the northern California Current system. We use qPCR to quantify the impact of doliolids on three important and globally abundant taxa: Synechococcus, SAR11 and diatoms. Doliolids were collected during bloom events identified at three different shelf locations with variable upwelling intensities. We discovered that in addition to eukaryotic phytoplankton, doliolids feed on a range of prokaryotic microbial functional groups. Prey included pelagic Archaea, Pelagibacter, and picocyanobacteria, expanding our understanding of doliolid feeding to the smallest and most numerous microbial community members of the ocean. We also found that doliolids retain SAR11, which is intriguing because some SAR11 lineages may evade predation by other benthic and pelagic tunicates through their surface properties. Given the ability of doliolids to clear large portions of seawater by filtration and their high abundance in this system, we suggest that doliolids are an important player in shaping microbial community structure, primary production, and carbon fate in an ecologically and economically important fisheries system

Production of a videotape series to promote forage-based livestock production in the Upper Midwest

Although properly managed grazing can increase farm income and enhance environmental quality, it has not been widely used in the Upper Midwest. Instead, grazing has been viewed as an adjunct to row crop production, and state-of-the-art management techniques have been adopted slowly. However, recent research has developed forage grazing systems that can compete economically with row crops, especially on more erodible land. In order to implement such systems successfully, producers need practical information on the technical aspects of grazing and pasture management. Most grazing videos produced prior to this project were tailored to other geographic regions or weren\u27t sufficiently detailed. The five videotapes produced in this project cover controlled grazing, principles for managing pasture plants, animal management, fencing and water systems, and year-round systems for the Upper Midwest

Once and Future Gulf of Mexico Ecosystem: Restoration Recommendations of an Expert Working Group

The Deepwater Horizon (DWH) well blowout released more petroleum hydrocarbons into the marine environment than any previous U.S. oil spill (4.9 million barrels), fouling marine life, damaging deep sea and shoreline habitats and causing closures of economically valuable fisheries in the Gulf of Mexico. A suite of pollutants—liquid and gaseous petroleum compounds plus chemical dispersants—poured into ecosystems that had already been stressed by overfishing, development and global climate change. Beyond the direct effects that were captured in dramatic photographs of oiled birds in the media, it is likely that there are subtle, delayed, indirect and potentially synergistic impacts of these widely dispersed, highly bioavailable and toxic hydrocarbons and chemical dispersants on marine life from pelicans to salt marsh grasses and to deep-sea animals. As tragic as the DWH blowout was, it has stimulated public interest in protecting this economically, socially and environmentally critical region. The 2010 Mabus Report, commissioned by President Barack Obama and written by the secretary of the Navy, provides a blueprint for restoring the Gulf that is bold, visionary and strategic. It is clear that we need not only to repair the damage left behind by the oil but also to go well beyond that to restore the anthropogenically stressed and declining Gulf ecosystems to prosperity-sustaining levels of historic productivity. For this report, we assembled a team of leading scientists with expertise in coastal and marine ecosystems and with experience in their restoration to identify strategies and specific actions that will revitalize and sustain the Gulf coastal economy. Because the DWH spill intervened in ecosystems that are intimately interconnected and already under stress, and will remain stressed from global climate change, we argue that restoration of the Gulf must go beyond the traditional "in-place, in-kind" restoration approach that targets specific damaged habitats or species. A sustainable restoration of the Gulf of Mexico after DWH must: 1. Recognize that ecosystem resilience has been compromised by multiple human interventions predating the DWH spill; 2. Acknowledge that significant future environmental change is inevitable and must be factored into restoration plans and actions for them to be durable; 3. Treat the Gulf as a complex and interconnected network of ecosystems from shoreline to deep sea; and 4. Recognize that human and ecosystem productivity in the Gulf are interdependent, and that human needs from and effects on the Gulf must be integral to restoration planning. With these principles in mind, the authors provide the scientific basis for a sustainable restoration program along three themes: 1. Assess and repair damage from DWH and other stresses on the Gulf; 2. Protect existing habitats and populations; and 3. Integrate sustainable human use with ecological processes in the Gulf of Mexico. Under these themes, 15 historically informed, adaptive, ecosystem-based restoration actions are presented to recover Gulf resources and rebuild the resilience of its ecosystem. The vision that guides our recommendations fundamentally imbeds the restoration actions within the context of the changing environment so as to achieve resilience of resources, human communities and the economy into the indefinite future