Reverberation from Deep Scattering Layers in the Western North Atlantic

Chapman, R. P.; Marshall, John R.

doi:10.1121/1.1910087

Cited by 29 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The aggregation of the mesopelagic micronekton within the HBL in the CC suggests that this fauna descends as deeply as possible to avoid visually orienting predators, while avoiding the effects of hypoxia. Off southern California, we did not observe deeper DSLs, in marked contrast to well-oxygenated regions of the world ocean, such as the South Pacific and North Atlantic oceans, where DSLs of mesopelagic fishes and other micronekton are regularly found at depths of 500 to 1000 m (Chapman & Marshall 1966, Williams & Koslow 1997.…”

Section: Discussionmentioning

confidence: 83%

Impact of declining intermediate-water oxygen on deepwater fishes in the California Current

Koslow¹,

Goericke²,

Lara‐Lopez³

et al. 2011

Mar. Ecol. Prog. Ser.

179

188

View full text Add to dashboard Cite

Although declining oxygen concentration has been reported for the oxygen minimum zones (OMZs) of the tropical oceans and the North Pacific Ocean, consistent with model predictions of the effects of global warming, its ecological impacts are poorly understood. We report the apparent impact of declining oxygen on midwater fishes within the OMZ of the southern California Current (CC). Principal component analysis of the California Cooperative Oceanic Fisheries Investigations (CalCOFI) ichthyoplankton time series from 1951 to 2008 indicates that the dominant temporal pattern (principal component 1 [PC1]) represents the marked decline of the region's mesopelagic fishes during periods of reduced oxygen. Of the 27 taxa with loadings > 0.5 on PC1, 24 were mesopelagic. PC1 was strongly correlated with intermediate-water oxygen concentrations (r = 0.75, p < 0.05), which were about 20% lower in the past decade and the 1950s than in the period from 1970 to 1995. The abundance of mesopelagic fishes represented by PC1 was reduced, on average, by 63% between periods of high and low oxygen concentrations. We hypothesize that the underlying mechanism is the shoaling of the hypoxic boundary layer during periods of reduced oxygen, which renders the mesopelagic fauna more vulnerable to visually orienting predators. The mesopelagic fish fauna provides a vital trophodynamic link between the marine plankton and many higher predators. The decline of deepwater fish populations has profound implications for commercial fisheries, marine food webs and marine conservation: climate models predict a 20 to 40% decline in global deepwater oxygen concentrations over the coming century.KEY WORDS: Oxygen · Mesopelagic fishes · Oxygen-minimum zone · Climate change · California CurrentResale or republication not permitted without written consent of the publisher

show abstract

Section: Discussionmentioning

confidence: 83%

Impact of declining intermediate-water oxygen on deepwater fishes in the California Current

Koslow¹,

Goericke²,

Lara‐Lopez³

et al. 2011

Mar. Ecol. Prog. Ser.

179

188

View full text Add to dashboard Cite

show abstract

“…The occurrence of a distinct lower DSL boundary in the southern California Current Ecosystem at depths shallower than in regions that lack an OMZ (Chapman & Marshall 1966, Williams & Koslow 1997, Bianchi et al 2013 suggests that most of the southern California mesopelagic community is bounded by an ecological threshold in the environment. Although a diverse group of metazoans has been found to reside within OMZ cores, this occurs primarily in regions with very shallow…”

Section: Bottom Boundarymentioning

confidence: 97%

Dissolved oxygen as a constraint on daytime deep scattering layer depth in the southern California current ecosystem

Netburn

Koslow

2015

Deep Sea Research Part I: Oceanographic Research Papers

View full text Add to dashboard Cite

“…Some of the data reported in Holliday (1977b) were collected with a seismic arcer as an acoustic source. Chapman and Marshall (1966) observed up to three resonance peaks in an aggregation of fish in the North Atlantic. Because the resonance frequency depends upon the volume of the swimbladder, which in turn is related to the size of the fish, the results suggested the presence of three size classes of fish.…”

Section: Introductionmentioning

confidence: 99%

“…Sizes of fish with swimbladders were originally studied and, in some cases, spectrally discriminated, through the use of broadband sound as early as the1940s by Hersey, Backus, and others, as briefly reviewed in Chapman and Marshall (1966). The work involved the use of broadband sound in the upper hundreds of hertz to low kilohertz frequencies to exploit the resonance of the swimbladder.…”

Section: Introductionmentioning

confidence: 99%

Resonance classification of mixed assemblages of fish with swimbladders using a modified commercial broadband acoustic echosounder at 1–6 kHz

Stanton

Sellers

Jech

2012

Can. J. Fish. Aquat. Sci.

View full text Add to dashboard Cite

Recently developed broadband acoustic methods were used to study mixed assemblages of fish spanning a wide range of lengths and species. Through a combination of resonance classification and pulse-compression signal processing, which provides for high-range resolution, a modified commercial broadband echosounder was demonstrated to provide quantitative information on the spatial distribution of the individual size classes within an assemblage. In essence, this system spectrally resolves the different size classes of fish that are otherwise not resolved spatially. This method reveals new insights into biological processes, such as predator-prey interactions, that are not obtainable through the use of a conventional narrowband high-frequency echosounder or previous broadband systems. A recent study at sea with this system revealed aggregations containing bladdered fish 15-30 cm in length (Atlantic herring (Clupea harengus) and silver hake (Merluccius bilinearis)) and a variety of species of smaller fish 2-5 cm in length. These observations infer that the smaller 2-5 cm fish can be colocated in the same aggregations as their predator, the larger silver hake, as well as pre-spawning herring. While this technological advancement provides more information, there remain challenges in interpreting the echo spectra in terms of meaningful biological quantities such as size distribution and species composition.Résumé : Des méthodes acoustiques à large bande récemment mises au point nous servent à étudier des peuplements mixtes de poissons couvrant un large éventail de longueurs et d'espèces. Par une combinaison de classification des résonances et de traitement des signaux de compression des impulsions qui fournit un haut degré de résolution, un échosondeur commercial modifié à large bande s'avère capable de fournir des données quantitatives sur la répartition spatiale des classes d'âge individuelles au sein d'un peuplement. Spécifiquement, le système permet une résolution spectrale des différentes classes de taille des poissons qui autrement ne peuvent être distinguées dans l'espace. La méthode ouvre de nouvelles perspectives sur les processus biologiques, tels que les interactions prédateurs-proies, qu'on ne peut obtenir par l'emploi d'un échosondeur ordinaire de haute fréquence à bande étroite, ni par les systèmes à large bande plus anciens. Une étude récente en mer avec ce système montre des rassemblements de poissons à vessie natatoire de longueurs de 15 à 30 cm (harengs atlantiques (Clupea harengus) et merlus argentés (Merluccius bilinearis)), ainsi qu'une variété d'espèces de poissons plus petits de longueurs de 2-5 cm. Ces observations laissent croire que les poissons plus petits de 2-5 cm peuvent être localisés ensemble dans les mêmes rassemblements que leurs prédateurs, les merlus de plus grande taille et les harengs avant la fraie. Bien que cette avancée technologique fournisse plus d'information, il reste des défis pour interpréter les spectres des rétrodiffusions en regard de quantités biologiques sig...

show abstract

Reverberation from Deep Scattering Layers in the Western North Atlantic

Cited by 29 publications

References 0 publications

Impact of declining intermediate-water oxygen on deepwater fishes in the California Current

Impact of declining intermediate-water oxygen on deepwater fishes in the California Current

Dissolved oxygen as a constraint on daytime deep scattering layer depth in the southern California current ecosystem

Resonance classification of mixed assemblages of fish with swimbladders using a modified commercial broadband acoustic echosounder at 1–6 kHz

Contact Info

Product

Resources

About