Seasonal and diurnal presence of finless porpoises at a corridor to the ocean from their habitat

Akamatsu, Tomonari; Nakamura, Keisuke; Kawabe, Ryo; Furukawa, Seishiro; Murata, Hiromi; Kawakubo, Akihiro; Komaba, Masayuki

doi:10.1007/s00227-010-1459-8

Cited by 23 publications

(11 citation statements)

References 17 publications

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“…These opposite trends may have been caused by climate and climaterelated environmental changes (Ohshimo et al 2009;Sakuramoto et al 2010;Yatsu et al 2005). Anchovies migrate in Omura Bay from the East China Sea to spawn in spring and spend their life in the bay until winter (Azeta 1981;Akamatsu et al 2010). Although no information is available on the origin of sardines in Omura Bay, it may be similar to that of anchovies.…”

Section: Discussionmentioning

confidence: 90%

The Response of Fish Communities to Climate and Human-Induced Changes Inferred from Fishery Landings in an Enclosed Bay

Chung

Suzaki

Kasai

et al. 2014

Estuaries and Coasts

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Variations in the fish community structure in Omura Bay, an enclosed bay in the East China Sea, were investigated using long-term fishery landing data over the past five decades . We confirmed that the fish community structure in Omura Bay showed three conspicuous regimes during the study period. Anchovies dominated in the pelagic domain with abundant and various demersal fish species in the first phase (1965)(1966)(1967)(1968)(1969)(1970)(1971)(1972)(1973)(1974)(1975)(1976)(1977)(1978). Demersal fish declined remarkably with the dominance of sardines in the pelagic domain during the second phase (1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987), and the fish community was simplified with the return of anchovies and no recovery of demersal fish in the third phase (1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006). These changes were significantly related with periodic largescale climate changes and cumulative regional-scale human impacts. The replacement of sardine/anchovy caused by a climate regime shift in the North Pacific contributed to the fish community regime shifts in Omura Bay. Moreover, habitat degradation such as depletion of dissolved oxygen combined with climate-induced changes in food web systems resulted in a rapid reduction in demersal fish. Contraction of the habitat volume due to an increase in oxygen-restricted water simplified the fish community structure and eventually reduced fishery landings in Omura Bay. These findings demonstrate that long-term fish community responses to largescale climate changes and regional-scale human impacts can be observed in a coastal enclosed bay, providing useful information for fisheries management in areas with climate and human-induced changes.

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Section: Discussionmentioning

confidence: 90%

The Response of Fish Communities to Climate and Human-Induced Changes Inferred from Fishery Landings in an Enclosed Bay

Chung

Suzaki

Kasai

et al. 2014

Estuaries and Coasts

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“…Long duration monitoring has not only increased the data availability of odontocete vocalizations but also provided information regarding the temporal variations of behavior and habitat utilization (e.g., Akamatsu et al, 2010;Soldevilla et al, 2011;Kimura et al, 2012;Lin et al, 2013a;Lin et al, 2015a). Therefore, the dynamic interactions of habitat utilization among sympatric odontocetes, which are essential information for the community ecology, can be studied by using a network of long duration recorders or marine observatories.…”

Section: Introductionmentioning

confidence: 99%

Automatic classification of delphinids based on the representative frequencies of whistles

Lin

Chou

2015

The Journal of the Acoustical Society of America

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Classification of odontocete species remains a challenging task for passive acoustic monitoring. Classifiers that have been developed use spectral features extracted from echolocation clicks and whistle contours. Most of these contour-based classifiers require complete contours to reduce measurement errors. Therefore, overlapping contours and partially detected contours in an automatic detection algorithm may increase the bias for contour-based classifiers. In this study, classification was conducted on each recording section without extracting individual contours. The local-max detector was used to extract representative frequencies of delphinid whistles and each section was divided into multiple non-overlapping fragments. Three acoustical parameters were measured from the distribution of representative frequencies in each fragment. By using the statistical features of the acoustical parameters and the percentage of overlapping whistles, correct classification rate of 70.3% was reached for the recordings of seven species (Tursiops truncatus, Delphinus delphis, Delphinus capensis, Peponocephala electra, Grampus griseus, Stenella longirostris longirostris, and Stenella attenuata) archived in MobySound.org. In addition, correct classification rate was not dramatically reduced in various simulated noise conditions. This algorithm can be employed in acoustic observatories to classify different delphinid species and facilitate future studies on the community ecology of odontocetes.

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“…2). The position of the A-tag was determined after consideration of the detection range (about 100 m for off-axis clicks of finless porpoise; Akamatsu et al 2010), the recommended maximum spacing for the pingers used (200 m; European Commission 2004), and the distance at which fishing operation can be achieved unobstructed. The daily encounters of finless porpoise obtained from the A-tag data fluctuated (see 'Results'), which implies that this site represents only a part of the home range of finless porpoises.…”

Section: Methodsmentioning

confidence: 99%

Long-term effectiveness of pingers on a small population of finless porpoises in Japan

Amano¹,

Kusumoto²,

Abe³

et al. 2017

Endang. Species. Res.

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Seasonal and diurnal presence of finless porpoises at a corridor to the ocean from their habitat

Cited by 23 publications

References 17 publications

The Response of Fish Communities to Climate and Human-Induced Changes Inferred from Fishery Landings in an Enclosed Bay

The Response of Fish Communities to Climate and Human-Induced Changes Inferred from Fishery Landings in an Enclosed Bay

Automatic classification of delphinids based on the representative frequencies of whistles

Long-term effectiveness of pingers on a small population of finless porpoises in Japan

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