Estimation of kelp forest, Laminaria spp., distributions in coastal waters of the Shiretoko Peninsula, Hokkaido, Japan, using echosounder and geostatistical analysis

Abstract

Sustainable management of the kelp forests of the Shiretoko Peninsula, a World Natural Heritage site, is necessary due to kelp's ecological and economic importance. The objectives of this study were to estimate the area of kelp forests and to clarify their spatial characteristics in coastal waters of the Shiretoko Peninsula. Data on the presence/absence and thickness of kelp forests were collected via acoustic observation on transects over about 80 km using a echosounder at 200 kHz. Acoustic data were geostatistically interpolated, and the areas covered by kelp forests were estimated. Differences in kelp distribution between the eastern and western sides of the peninsula were compared. The total area of kelp forest was 3.88 km 2 (eastern area: 3.49 km 2 ; western area: 0.39 km 2 ). The range of thickness of the kelp forests was 34-91 cm. Many kelp forests in the eastern area were thick (>78 cm) and distributed continuously, while kelp forests in the western area were sparsely distributed.

Assessing the low frequency acoustic characteristics of Macrocystis pyrifera, Egregia menziessi, and Laminaria solidungula

“…For instance, the first trial of this experiment used a specimen with the fewest number of individual pneumatocysts (6) and the smallest volume of air (4.9 ml), but this segment exhibited the greatest acoustic change upon air removal. The third trial contained a frond segment with the highest number of pneumatocysts (12) and greatest volume of air 5.7 ml, yet this frond segment exhibited the least acoustic change upon air removal. The results of these trials suggest that the tissue component of individual frond sections may be more important than simply the number and size of air-filled pneumatocysts.…”

“…To date, acoustic methods are only used to delineate the boundaries of kelp forests in horizontal and vertical space. [9][10][11][12][13] Although these methods provide a useful assessment of boundary changes in forests through time, 10 scientists still lack the capability to reliably assess total biomass, density, or the physiological condition of kelp fronds using existing acoustic methods.…”

“…Although an increasing number of studies are effectively relating observed acoustic signatures to visual observations obtained from diver surveys and underwater video systems, no study has yet attempted to develop a mechanistic understanding of the interaction between sound energy and kelp morphology. [9][10][11][12][13] Furthermore, current acoustic surveys of kelp forests provide information on horizontal and vertical forest boundaries, but are presently unable to assess kelp biomass or physiological condition.…”

Predicting spatial kelp abundance in shallow coastal waters using the acoustic ground discrimination system RoxAnn

“…Parnum et al, 2009;Rattray et al (2009), Ierodiaconou et al (2011), McGonigle et al (2011), andvan Rein et al (2011), for example, used MBES and partially also sidescan sonar to identify benthic habitats and discriminate between different seaweed species in water depth of w40 m. While it was simple to distinguish between physical habitats, discrimination between biological habitats was still afflicted with uncertainties (e.g. Méléder et al, 2010;Minami et al, 2010).…”

“…Kruss et al, 2006;Méléder et al, 2010;Minami et al, 2010). These investigations reveal that there are still problems in classifying gradual changes in seafloor environments which often occur in nature (Pinn and Robertson, 2003).…”