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Accurate efficient estimation of actual and potential species distribution is a critical requirement for effective ecosystem-based management and marine protected area design. In this study we tested the applicability of a terrestrial landscape modeling technique in a marine environ- ment for predicting the distribution of ecologically and economically important groundfish, using 3 species of rockfish at Cordell Bank National Marine Sanctuary (CBNMS) as a model system. Auto- classification of multibeam bathymetry along with georeferenced submersible video transect data of the seafloor and demersal fishes were used to model the abundance and distribution of rockfish. Gen- eralized linear models (GLMs) were created using habitat classification analyses of high-resolution (3 m) digital elevation models combined with fish presence/absence observations. Model accuracy was assessed using a reserved subset of the observation data. The resulting probability of occurrence models generated at 3 m resolution for the entire 120 km 2 study area proved reliable in predicting the distribution of all the species. The accuracies of the models for Sebastes rosaceus, S. flavidus and S. elongatus were 96, 92 and 92%, respectively. The probability of occurrence of S. flavidus and S. rosaceus was highest in the high relief rocky areas and lowest in the low relief, soft sediment areas. The model for S. elongatus had an opposite pattern, with the highest predicted probability of occur- rence taking place in the low relief, soft sediment areas and a lower probability of occurrence in the rocky areas. These results indicate that site-specific and species-specific algorithmic habitat classifi- cation applied to high-resolution bathymetry data can be used to accurately extrapolate the results from in situ video surveys of demersal fishes across broad areas of habitat.

Due to the decline of fisheries throughout the world, there is an ever-increasing demand among fisheries managers for more and better data regarding the distribution and abundance of commercially important fishes. Along the Pacific coast of North America, there are insufficient stock data for most rockfish species, which compose one of the most valuable commercial and recreational fisheries in California. One approach being explored for increasing our understanding of fish distribution patterns and potentially generating stock assessment data over large areas is the use of habitat-based assessment. The general hypothesis is that because rockfish are not randomly distributed across habitats, it should be possible to model and predict their distribution and abundance based on habitat maps and biological data. Furthermore, to the extent that these models are robust and portable, they should be applicable across a variety of locations and physical settings. We attempt to test these hypotheses using predictive...

Time serial multibeam bathymetry is used to evaluate geomorphic trends and submarine processes in the upper 4 km of Monterey Canyon, California. Seven high-resolution bathymetric surveys conducted between September 2002 to February 2005 show that the upper canyon axis and head grew in volume 1 000 000 m3 ± 700 000 m3, at an average annual rate of 400 000 m3/a ± 300 000 m3/a through lateral erosion and vertical incision. This net loss of substrate during the 29-month period is parsed between local erosion of 1 400 000 m3 and local deposition of 350 000 m3. A submarine landslide with a scar void volume of 70 000 m3 and debris pile of 52 000 m3 occurred between March 2003 and September 2004. During the subsequent months until February 2005, the slide scar grew 40% in volume while the debris pile shrank by 80%. The canyon-head rim adjacent to Moss Landing Harbor prograded seaward and retreated shoreward significantly (up to 50 m) during the study suggesting frequent episodes of sediment build up and subsequent down-canyon failure. A large field of sand waves located in the channel axis was completely reworked in each time series except for a 24 h period where no wave crest movement was noted, and a 32 day period where up-canyon migration of approximately 7 m was recorded in the northern tributary.

There is a great need for accurate, comprehensive maps of seafloor habitat for use in fish stock assessments, marine protected area design, and other resource management pursuits. Recent advances in acoustic remote sensing technology have made it possible to obtain high-resolution (meter to sub-meter) digital elevation models (DEMs) of seafloor bathymetry that can rival or surpass those available for the terrestrial environment. The acquisition and processing of these data are expensive, however, requiring specialized equipment, expertise, and large amounts of both field and laboratory effort per unit area mapped. Further, the interpretation and classification of these data into maps of habitat type is typically (and appropriately) performed only by trained experts that are familiar with both seafloor geomorphology and the nature and limitations of the data sources. Because it is done visually, this interpretation can be very time-consuming and may yield subjective results that are not comparable from site-to-site or between individual interpreters.We applied an algorithmic terrain analysis approach to efficiently and objectively classify seafloor habitats using the quantifiable landscape metric Topographic Position Index (TPI). We used high-resolution multibeam bathymetry, together with precisely geolocated (± 5 m) ROV observations of fish distribution, to produce a preliminary genus-specific habitat suitability model for eight rockfish (Sebastes) species in the Del Monte shale beds of Monterey Bay, California. A high-resolution (2 m) multibeam bathymetry Digital Elevation Model (DEM) was generated and used to produce a derived TPI surface model using repeatable, algorithmic methods. This data layer, together with the positions and counts by species from 229 rockfish observations (2892 total fish) was then used to create preliminary predictive models of habitat suitability and fish distribution, as well as stock estimates for the study area. A second, independent fish observation data set was used to validate the models.

The squid Loligo opalescens lays its eggs in capsules attached to a flat sandy substrate. These capsules are usually clustered in so‐called egg beds. Earlier work in Monterey Bay, CA [Foote et al., J. Acoust. Soc. Am. 119, 844–856 (2006)] established the acoustic detectability of such egg beds. This work has now been extended in a new study performed in June 2006. An EdgeTech sidescan sonar was towed at nominal 5‐m height over the bottom. Measurements were made at 400 kHz, horizontal beamwidth 0.5 deg, along six parallel transects, with adjacent centerlines separated by 30 m. The swath width along each transect was 100 m. The transects were repeated on 10, 13, and 14 June. Data from areas where egg beds were densely concentrated, confirmed by drop video camera, have been excerpted. Comparisons of corresponding data, which are generally very strong, are quantified. The question is asked as to whether such sidescan sonar data can be used differentially to measure egg‐laying success or hatching over rather short periods of time. If so, this could be a useful tool both in ecological studies and for management purposes. [Work supported by NURP.]

Publisher pdf: http://dx.doi.org/10.1121/1.2149840. Journal home page: http://scitation.aip.org/jasa/ The squid Loligo opalescens is a key species in the nearshore pelagic community of California, supporting the most valuable state marine fishery, yet the stock biomass is unknown. In southern Monterey Bay, extensive beds occur on a flat, sandy bottom, water depths 20–60 m, thus sidescan sonar is a prima-facie candidate for use in rapid, synoptic, and noninvasive surveying. The present study describes development of an acoustic method to detect, identify, and quantify squid egg beds by means of high-frequency sidescan-sonar imagery. Verification of the method has been undertaken with a video camera carried on a remotely operated vehicle. It has been established that sidescan sonar images can be used to predict the presence or absence of squid egg beds. The lower size limit of detectability of an isolated egg bed is about 0.5 m with a 400-kHz sidescan sonar used with a 50-m range when towed at 3 knots. It is possible to estimate the abundance of eggs in a region of interest by computing the cumulative area covered by the egg beds according to the sidescan sonar image. In a selected quadrat one arc second on each side, the estimated number of eggs was 36.5 million.

Recently acquired 3-m-resolution 244 kHz multibeam seafloor bathymetry (0.5 m depth precision) reveals geomorphology at sufficient detail to interpret small-scale features and short-term processes in the upper 4 km of Monterey Canyon, California. The study area includes the continental shelf and canyon features from 10 m to 250 m depth. The canyon floor contains an axial channel laterally bounded by elevated complex terrace surfaces. Sand waves with 2 m height and 35 m average wavelength dominate the active part of the canyon floor. The sand waves are strongly asymmetrical, indicating net down-canyon sediment transport in this reach. Terraces, including a broad 25-m-tall terrace complex near the head of the canyon, bear evidence of recent degradation of the canyon floor. Slump scars and gullies having a variety of sizes and relative ages shape the canyon walls. Serial georeferenced digital elevation models were analyzed to detect net changes in bathymetry or morphology occurring during both a six month period (September 2002 to March 2003) and a 24-h period (24 March to 25 March). Significant changes over the six month period include: (1) complete reorganization of the sand waves on the channel floor, (2) local channel degradation creating new 2-m-tall erosional terraces on the channel margins, (3) local channel widening that laterally eroded older channel margin terraces, and (4) 60 m extension of one minor gully head on a steep canyon wall. There were no discernable changes in morphology during the 24-h study period. Raster subtraction of serial bathymetric grids provides estimates of sediment erosion and deposition that occurred between the canyon head and a point 2 km down canyon during the six month study. Erosion of 320,000 m 3 (±80,000 m 3 ) of sediment occurred mainly in the tributaries, along the margins of the axial channel, and in the lowest 700 m of the analyzed reach. This eroded volume was approximately balanced by 260,000 m 3 (±70,000 m 3 ) of sediment deposition that was concentrated in the nearshore region along the rim of the canyon head. There was no measurable sediment gain or loss during the 24-h study period.

Clusters of gelatinous egg capsules, known as mops or beds, of the market squid (Loligo opalescens) were mapped in a shallow‐water, sandy habitat of Monterey Bay, California. The benthic egg clusters were imaged using an EdgeTech 272‐TD dual‐frequency sidescan sonar towed from R/V MacGinitie, an 8‐m‐long survey vessel, with data recorded on a Triton Elics International Isis digital data acquisition system. Verification of target identity was accomplished independently by video photography from a remotely operated vehicle. The survey area included a 4‐km stretch of sandy seafloor between Lover’s Point and Cannery Row in Monterey at depths of 15–30 m. The study area had previously been mapped using the RESON SeaBat 8101 240‐kHz multibeam sonar. Resulting high‐resolution bathymetric data, with 1‐m resolution, were used during the survey planning and execution. Squid egg clusters were clearly visible in the very‐high‐resolution, 400‐kHz backscatter imagery, with pixel size 10–20 cm, recorded from the towed si...

Management of declining rockfish stocks requires effective tools capable of providing accurate stock assessments of near‐shore, high‐relief habitat. Multibeam bathymetry, when analyzed with GIS landscape analysis tools, can create models which can identify preferred habitat based on species‐specific parameters. For this study, high‐resolution multibeam data of the Del Monte shale beds in Monterey Bay, California were analyzed in GIS for slope, rugosity, and relative topographic position to assess rockfish (Sebastes spp.) habitat preference. Video transects collected by a remotely operated vehicle (ROV) provided habitat ground‐truth and fish distribution data. A series of habitat suitability models was created in GIS by combining different suitability factors from multibeam‐derived grids: slope, rugosity, topographic position index (TPI), and depth. Distance to preferred categories for each parameter were determined for eight rockfish species. Of these, distance to peak features identified by TPI50 proved the most effective means of modeling fish distribution, successfully predicting an average of 80% of the eight rockfish species. Using fish distribution information, stock estimates were calculated for the study area. By combining GIS landscape analysis tools with multibeam bathymetry and ROV video data, we have created a predictive tool that can locate areas of most suitable habitat given rockfish‐specific parameters.