Alex Hearn

Residency of the scalloped hammerhead shark (Sphyrna lewini) at Malpelo Island and evidence of migration to other islands in the Eastern Tropical Pacific

Sixty nine hammerhead sharks, Sphyrna lewini, were tagged at Malpelo Island (Colombia) with ultrasonic transmitters during March 2006, 2007 and 2008, as part of a study to understand their residency at the island and their horizontal and vertical movements. Five sharks visited Cocos Island, 627 km distant from Malpelo. One of the sharks that appeared at Cocos Island also visited the Galapagos Islands, 710 km from Cocos, a month later. There is connectivity of Sphyrna lewini between Malpelo, Cocos and the Galapagos Islands, but the frequency of movements between the islands appears to be relatively low (<7% of the tagged sharks). The most common depth at which the sharks swam coincided with the thermocline (rs = 0.72, p < 0.01). The depth of the thermocline varied depending on the time of the year. Nocturnal detections of the sharks were more frequent during the cold season than during the warm season (W = 60, p < 0.01). We also found that hammerheads spent significantly more time on the up-current side of the island (Kruskal-Wallis = 31.1008; p < 0.01). This study contributes to the knowledge of hammerhead sharks not only in Malpelo Island but also at a regional level in the Eastern Tropical Pacific.

Diel movements of out-migrating Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) smolts in the Sacramento/San Joaquin watershed

We used ultrasonic telemetry to describe the movement patterns of late-fall run Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (O. mykiss) smolts during their entire emigration down California’s Sacramento River, through the San Francisco Bay Estuary and into the Pacific Ocean. Yearling hatchery smolts were tagged via intracoelomic surgical implantation with coded ultrasonic tags. They were then released at four upriver locations in the Sacramento River during the winters of 2007 through 2010. Late-fall run Chinook salmon smolts exhibited a nocturnal pattern of migration after release in the upper river. This is likely because individuals remain within a confined area during the day, while they become active at night and migrate downstream. The ratio between night and day detections of Chinook salmon smolts decreased with distance traveled downriver. There was a significant preference for nocturnal migration in every reach of the river except the Estuary. In contrast, steelhead smolts, which reside upriver longer following release, exhibited a less pronounced diel pattern during their entire migration. In the middle river, Delta, and Estuary, steelhead exhibited a significant preference for daytime travel. In the ocean Chinook salmon preferred to travel at night, yet steelhead were detected on the monitors equally during the night and day. These data show that closely related Oncorhynchus species, with the same ontogenetic pattern of out-migrating as yearlings, vary in migration tactic.

Performance of an ultrasonic telemetry positioning system under varied environmental conditions

BackgroundAdvances in ultrasonic telemetry, including the ability to accurately position a transmitter within an array of hydrophone receivers, have led to increased opportunities to investigate a broad spectrum of ecological questions in aquatic systems. The quality and efficiency of positioning a transmitter relies upon factors controlled by the researcher (for example, geometry of the receiver array) as well as environmental conditions (for example, water quality or environmental noise). While the physics of sound wave propagation are well understood, the high amount of environmental variability in and among aquatic habitats makes it difficult to predict exactly how any given ultrasonic signal will behave. To evaluate variability in system performance across different receiver arrays in diverse environments we present positional records for fixed-location tags recorded with a popular positioning array, the VEMCO Positioning System (VPS). Using these records we evaluate the relationships between system performance, measured as both horizontal positioning error and positioning efficiency, and user-controlled and environmental variables. We used generalized linear mixed models to assess performance at a coastal site, a site in a freshwater tidal estuary, and a riverine site.ResultsThe positioning errors were similar across sites, with median errors ranging from 1.6 to 3.3 m. In contrast, there was large variation in positioning efficiency across sites, with poor positioning efficiency in the coastal habitat (7%), possibly due to high levels of bioacoustic noise, and moderate efficiency in the river (21%) and estuary habitats (27%). Our statistical models indicate that array geometry was consistently the most important predictor of positioning performance. Environmental noise and water movement also emerged as additional predictors of performance at several sites.ConclusionsThe results provide insight into VPS performance capabilities and emphasize the importance of testing array geometries. Additionally, water quality parameters should be monitored and receiver mooring designs should be carefully considered before embarking upon a telemetry study. We hope this work will guide future researchers in creating more effective designs for positioning arrays, and facilitate the collection of high quality information about movement and behavior patterns of aquatic organisms.

Elasmobranchs of the Galapagos Marine Reserve

The Galapagos Marine Reserve is home to at least 50 species of sharks and rays. Although these species are protected in the marine reserve, they are vulnerable to industrial fishing outside the protected waters, to unintentional bycatch by local fishers inside the reserve, and to illegal fishing. Our knowledge of shark ecology in Galapagos has increased dramatically in the last decade, due to the creation of an interinstitutional research program, which focuses on the spatial ecology of hammerhead and whale sharks. Hammerheads are resident at restricted locations where they school during the day and disperse to sea most nights. Alternatively, mostly large, pregnant female whale sharks visit the northern islands from June through November for only a few days, as part of a large-scale migration.

Behavior, movements, and habitat use of adult green sturgeon, Acipenser medirostris, in the upper Sacramento River

We conducted the first continuous shipboard tracking of southern Distinct Population Segment green sturgeon, Acipenser medirostris, in the Sacramento River. Tracking of adult green sturgeon occurred between river kilometer (rkm) 434.8 and 511.6, a section of the putative spawning grounds located near Red Bluff, California. The recorded positions of acoustically tagged green sturgeon were analyzed using First Passage Time analysis to determine differences in habitat use between suitable and non-suitable habitats. Classification and Regression Tree modeling was used to determine explanatory inputs attributable to above average habitat use. Green sturgeon exhibited above average habitat use at five sites, identified as potential spawning aggregate sites. Three types of movements (holding, milling, and directed) could be categorized from tracks. Lastly, we show that green sturgeon while on the spawning grounds exhibit a high degree of mobility throughout the spawning grounds, often making large movements between specific habitat units. Our study illustrates how the application of shipboard tracking can be useful for describing movement, behavior and habitat utilization at a spatial scale not achieved by stationary acoustic monitors.

Undersea Constellations: The Global Biology of an Endangered Marine Megavertebrate Further Informed through Citizen Science

The whale shark is an ideal flagship species for citizen science projects because of its charismatic nature, its size, and the associated ecotourism ventures focusing on the species at numerous coastal aggregation sites. An online database of whale shark encounters, identifying individuals on the basis of their unique skin patterning, captured almost 30,000 whale shark encounter reports from 1992 to 2014, with more than 6000 individuals identified from 54 countries. During this time, the number of known whale shark aggregation sites (hotspots) increased from 13 to 20. Examination of photo-identification data at a global scale revealed a skewed sex-ratio bias toward males (overall, more than 66%) and high site fidelity among individuals, with limited movements of sharks between neighboring countries but no records confirming large, ocean basin-scale migrations. Citizen science has been vital in amassing large spatial and temporal data sets to elucidate key aspects of whale shark life history and demographics and will continue to provide substantial long-term value.

First record of the southern ocean sunfish, Mola ramsayi , in the Galápagos Marine Reserve

tierney m. thys, jonathan whitney, alex hearn, kevin c. weng, cesar pen~aherrera, l. jawad, j. alfaro-shigueto, j.c. mangel and stephen a. karl Ocean Sunfish Research and Tagging Program, 25517 Hacienda Place, Suite C Carmel, CA, 93923, Hawai’i Institute of Marine Biology, University of Hawai’i, Mānoa, PO Box 1346, Kāne’ohe, HI, 96744, Department of Wildlife, Fish, and Conservation Biology, 1088 Academic Surge, University of California, Davis, One Shields Avenue, Davis, CA, 95616-5270, Oceanography Department, Pelagic Fisheries Research Program, University of Hawai’i, Mānoa, Honolulu, HI 96822, Charles Darwin Foundation, Puerto Ayora, Santa Cruz Island, Galapagos, Ecuador, Natural Sciences, Auckland War Memorial Museum, Tamaki Paenga Hira, The Domain, Private Bag 92018, Victoria Street West, Auckland 1142, New Zealand, Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Cornwall Campus, TR10 9EZ, UK

Echinoderms of Ecuador

This chapter presents a summary of studies on echinoderms on the Ecuadorian continental shelf and at the Galapagos Islands. The geographic, climatic and oceanographic contexts, as well as the general characteristics of ecosystems and communities are discussed first to better understand the diversity of echinoderms and their distribution in Ecuador. The research section is divided into six subsections: (1) diversity and distribution of echinoderm species on the Ecuadorian Continental Shelf and at the Galapagos Islands; (2) ecology and population biology (distribution, density, growth, size structure, allometric scaling, reproduction, diet and feeding habits) for three species of sea cucumbers, seven species of sea urchins, and three species of sea stars; (3) effects of temperature on the immune response of the sea urchin Echinometra vanbrunti, with emphasis during El Nino episode of 1997–1998 in the Ecuadorian coast; (4) distribution and abundance of ophiopluteus and echinopluteus larvae; (5) predation, parasitism, and ecology disease for some echinoderms, including the sand dollar Encope micropora, the starfish Phataria unifascialis, the sea urchin Eucidaris galapagensis, and two families of aspidochirote holothurians; and (6) interacting effects of sea urchins on benthic communities. Three sections consider echinoderm fisheries and aquaculture, their threats, with special emphasis on the conservation of echinoderms in Ecuador. The final section contains suggestions and recommendations.

Movements of steelhead (Oncorhynchus mykiss) smolts migrating through the San Francisco Bay Estuary

We used acoustic telemetry to monitor the out-migration of 1,000 steelhead smolts (Oncorhynchus mykiss) through the San Francisco Bay Estuary during spring of 2009 and 2010. The smolts transited the estuary rapidly (2–4 days) and utilized flows in the main channel during their migration. Fewer smolts were detected in marinas, tributaries and other shallow areas surrounding the estuary. Many of the smolts made repeated upriver and downriver movements that were related to the tidal flow, moving upstream during flood tides and downstream during ebb tides. These results show that steelhead smolts migrating from the Sacramento River transit rapidly through the lower reaches and do not use the estuary for feeding, rearing, or smoltification purposes.