In situ measurements of acoustic target strengths of gas-bearing siphonophores

Warren, Joseph D.; Stanton, Timothy K.; Benfield, Mark C.; Wiebe, Peter H.; Chu, Dezhang; Sutor, Malinda

doi:10.1006/jmsc.2001.1047

Cited by 62 publications

(40 citation statements)

References 23 publications

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“…Siphonophores were collected at depths of up to 180m during trawls at the Mona Passage, indicating that they are present in this area. Unfortunately, the ADCP frequency used for DSL detection in Mona Passage study (76.8kHz) (Rovira-Peña, 2006) was higher than the most useful frequency for detecting siphonophores (24.5kHz) (Warren et al, 2001), and so acoustic documentation of siphonophore vertical movement patterns are not available at this site. Other potential gelatinous prey for leatherbacks in the Eastern Caribbean Sea include the white-spotted jellyfish (Phyllorhiza punctata) (Garcia and Durban, 1993), pink meanie (Drymonema dalmatinum) (Williams et al, 2001) and moon jellyfish (Aurelia aurita) (Iverson and Skinner, 2006).…”

Section: Discussionmentioning

confidence: 99%

Diel foraging behavior of gravid leatherback sea turtles in deep waters of the Caribbean Sea

Casey

Garner

et al. 2010

Journal of Experimental Biology

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SUMMARYIt is generally assumed that leatherback turtles (Dermochelys coriacea), like other species of sea turtle, do not feed while offshore from nesting beaches, and rely instead on fat reserves to fuel reproductive activities. Recent studies, however, provide evidence that leatherbacks may forage during the internesting interval while offshore in the Western Atlantic Ocean and Caribbean Sea. Bio-logging technology was used to investigate the foraging behavior of female leatherback turtles at St Croix, US Virgin Islands. Leatherback gastrointestinal tract temperatures (T GT ) were analyzed for sudden fluctuations indicative of ingestions, and laboratory ingestion simulations were used to characterize temperature fluctuations associated with ingestion of prey versus seawater. Dive patterns associated with prey ingestion were characterized and the proportion of prey ingestion during the day (05:00-18:59h) and night (19:00-04:59h) were compared. A combined total of 111 prey ingestions for seven leatherback turtles were documented during the internesting interval. The number of prey ingestions ranged from six to 48 for individual turtles, and the majority (87.4%) of these events occurred during the daytime. Prey ingestions were most frequently associated with V-shaped dives, and the mean (±1s.d.) maximum dive depth with prey ingestion ranged from 154±51 to 232±101m for individual turtles. Although leatherbacks were found to opportunistically feed during the internesting interval, the low prey ingestion rates indicate that energy reserves acquired prior to the breeding season are critical for successful reproduction by leatherbacks from the St Croix, USVI nesting population.

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Section: Discussionmentioning

confidence: 99%

Diel foraging behavior of gravid leatherback sea turtles in deep waters of the Caribbean Sea

Casey

Garner

et al. 2010

Journal of Experimental Biology

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“…Conversely, large crustaceans, squids and non-gas bearing fishes, are relatively weak scatterers at this frequency (Lavery et al, 2002;Kang et al, 2005) and their importance to total backscatter in this study was likely small. Gelatinous organisms with pneumatophores may also be important sources of scattering at 38 kHz (Warren et al, 2001). Bongo net catches indicate that pteropods, siphonophores, and salpids are not abundant in the surface waters around Condor and at a nearby open-water site , and their scattering would have been masked by the much stronger scattering of the dominant swimbladdered fish.…”

Section: Data Processingmentioning

confidence: 99%

Persistent Enhancement of Micronekton Backscatter at the Summits of Seamounts in the Azores

et al. 2017

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Knowledge of the dynamics of micronekton at seamounts is critical to understanding the ecological role of these ecosystems. Active acoustic techniques are an effective tool to monitor the distribution and movements of pelagic organisms. We carried out several day-and nighttime active acoustic surveys over a 3-year period (2009)(2010)(2011) to characterize the spatial and temporal distribution of micronekton backscatter on two seamounts (Condor and Gigante) in the Azores and in the surrounding open-waters. The highest mean volume backscattering strength (MVBS) was consistently found in the water column over the seamount summits, regardless of the season and diel period. MVBS over the summits was 14-26 times higher than over the slopes, and 10 times higher than in open-waters. Diel variations in backscatter intensity were more pronounced in open-waters and in Gigante seamount, with higher values during the day in open-waters, and at night over the summits and slopes of Gigante. Over Condor seamount, diel changes in backscatter intensity were small, but MVBS was generally higher at night than during the day, as in Gigante. Persistence of strong acoustic backscatter over the summits of Condor and Gigante seamounts is a key finding of this study and may be explained by the presence of a seamount-associated micronekton community and by the retention of vertically migrating micronekton. The latter hypothesis is consistent with observed day-night differences in backscatter, suggesting that nocturnal migrants may be passively transported or actively swim above seamount summits and slopes. Possible physical mechanisms leading to the observed patterns in micronekton distribution are discussed. This study contributes to a better understanding of how seamounts may influence the spatial and temporal dynamics of micronekton assemblages.

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“…2, and next paragraph). Our net samples did not reveal other planktonic organisms that are strong sound scatterers and sometimes abundant in the Gulf of Maine, such as siphonophores (which can leave a trace when nets are pulled slowly, as in vertical tows) and pteropods (which would be retained by the nets) (De Robertis 2001, Warren et al 2001.…”

Section: Zooplanktonmentioning

confidence: 73%

Trophic relationships and oceanography on and around a small offshore bank

Stevick¹,

Incze²,

Kraus³

et al. 2008

Mar. Ecol. Prog. Ser.

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Small offshore banks may be sites of intense feeding by upper trophic level predators. We studied the distribution of cetaceans, seabirds, pelagic fish, euphausiids and zooplankton over a 9 × 15 km bank to determine the conditions and processes that concentrated prey there and to examine the relative importance of bottom-up or top-down controls. Euphausiids were the primary prey during most foraging activity. While these were widespread in subsurface waters, foraging was concentrated on dense surface swarms that formed during daylight hours over 2 small crests. Internal wave passage resulted in upward movement and concentration of euphausiids in these areas through a coupling of physical processes and euphausiid behavior, resulting in surface swarms. Thus, internal waves appear to provide a critical mechanism enhancing trophic energy transfer. The formation of dense, localized and accessible prey concentrations was more important to foraging than was the overall available prey biomass. The estimated maximum daily consumption of euphausiids by cetaceans, seabirds and herring combined was < 0.4% of the estimated instantaneous euphausiid biomass, and top-down control was unlikely to have substantially influenced euphausiid biomass at this site. Some predator species that do not prey extensively on euphausiids or herring were more prevalent in off-bank waters. The scales of predictability and the temporal dynamics of such features determine the manner in which populations of upper trophic level organisms utilize a variable environment.KEY WORDS: Foraging ecology · Euphausiid · Internal wave · Consumption · Cetacean · SeabirdResale or republication not permitted without written consent of the publisher

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In situ measurements of acoustic target strengths of gas-bearing siphonophores

Cited by 62 publications

References 23 publications

Diel foraging behavior of gravid leatherback sea turtles in deep waters of the Caribbean Sea

Diel foraging behavior of gravid leatherback sea turtles in deep waters of the Caribbean Sea

Persistent Enhancement of Micronekton Backscatter at the Summits of Seamounts in the Azores

Trophic relationships and oceanography on and around a small offshore bank

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