Essential Fish Habitat project status report

: Groundfish that associate with rugged seafloor types are difficult to assess with bottom-trawl sampling gear. Simrad ME70 multibeam echosounder (MBES) data and video imagery were collected to characterize trawlable and untrawlable areas, and to ultimately improve efforts to determine habitat-specific groundfish biomass. The data were collected during two acoustic-trawl surveys of the Gulf of Alaska (GOA) during 2011 and 2012 by NOAA Alaska Fisheries Science Center (AFSC) researchers. MBES data were collected continuously along the trackline, which included parallel transects (1-20 nmi spacing) and fine-scale survey locations in 2011. Video data were collected at camera stations using a drop camera system. Multibeamderived seafloor metrics were overlaid with the locations of previously conducted AFSC bottomtrawl (BT) survey hauls and 2011 camera stations. Generalized linear models were used to identify the best combination of multibeam metrics to discriminate between trawlable and untrawlable seafloor for the region of overlap between the camera stations or haul paths and the MBES data. The most discriminatory models were chosen based on the Akaike information criterion (AIC). The two best models were developed using data collected at camera stations with either oblique incidence backscatter strength (Sb) or mosaic Sb in combination with bathymetric position index and seafloor ruggedness and described over 54% of the variation between trawlable and untrawlable seafloor types. A map of predicted seafloor trawlability produced from the model using mosaic Sb and benthic-terrain metrics demonstrated that 58% of the area mapped (5,987 km2 ) had \u3e 50% probability of being trawlable and 42% of being untrawlable. The model predicted 69% of trawlable and untrawlable haul locations correctly. Successful hauls occurred in areas with 62% probability of being trawlable and haul locations with gear damage occurred in areas with a 38% probability of being trawlable. This model and map produced from multibeamderived seafloor metrics may be used to refine seafloor interpretation for the AFSC BT surveys and to advance efforts to develop habitat-specific biomass estimates for GOA groundfish populations

Seabed classification for trawlability determined with a multibeam echo sounder on Snakehead Bank in the Gulf of Alaska

Rockfishes (Sebastes spp.) tend to aggregate near rocky, cobble, or generally rugged areas that are difficult to survey with bottom trawls, and evidence indicates that assemblages of rockfish species may differ between areas accessible to trawling and those areas that are not. Consequently, it is important to determine grounds that are trawlable or untrawlable so that the areas where trawl survey results should be applied are accurately identified. To this end, we used multibeam echosounder data to generate metrics that describe the seafloor: backscatter strength at normal and oblique incidence angles, the variation of the angle-dependent backscatter strength within 10° of normal incidence, the scintillation of the acoustic intensity scattered from the seafloor, and the seafloor rugosity. We used these metrics to develop a binary classification scheme to estimate where the seafloor is expected to be trawlable. The multibeam echosounder data were verified through analyses of video and still images collected with a stereo drop camera and a remotely operated vehicle in a study at Snakehead Bank, ~100 km south of Kodiak Island in the Gulf of Alaska. Comparisons of different combinations of metrics derived from the multibeam data indicated that the oblique-incidence backscatter strength was the most accurate estimator of trawlability at Snakehead Bank and that the addition of other metrics provided only marginal improvements. If successful on a wider scale in the Gulf of Alaska, this acoustic remote-sensing technique, or a similar one, could help improve the accuracy of rockfish stock assessments

National Oceanic and Atmospheric Administration Report 121

From introduction: This report is a summary of presentations and discussions from a workshop on automated image processing conducted in Seattle, Washington, from 4-7 September, 2010. The objective of the workshop was to examine current and future applications of automated image processing for fisheries and marine ecology research

Seafloor Characterization for Trawlability and Fish Habitat Using the Simrad ME70 Multibeam Echosounder in the Gulf of Alaska

Rockfish (Sebastes spp.) stocks that associate with rugged seafloor types are difficult to assess due to limitations of traditional bottom-trawl sampling gear. Alternative methods that include acoustic remote sensing and video imagery may improve stock assessment in untrawlable locations. Acoustics can also be applied to identify locations where alternative assessment methods are required. We use the Simrad ME70 multibeam echosounder (ME70) and trawl survey performance data to develop a seafloor trawlability classification scheme for locations in the Gulf of Alaska (GOA). We surveyed areas of the GOA (20-500 m depth) using the ME70 aboard the NOAA ship Oscar Dyson during summer 2011. Seafloor parameters derived from the ME70 data were used to classify seafloor trawlability including, the average backscatter measured as a function of incidence angle, scintillation index from the backscatter, and seafloor rugosity from the depth soundings. We present a preliminary seafloor trawlability classification for areas of the GOA. The next phase of this work will characterize seafloor habitats for harvested species in our survey area using ME70 data, video imagery, and species occurrence data from the trawl survey

Seafloor Characterization for Trawlability and Fish Habitat Using the Simrad ME70 Multibeam Echosounder in the Gulf of Alaska

Groundfish that associate with rugged seafloor types are difficult to assess with bottom-trawl sampling gear. Simrad ME70 multibeam echosounder (ME70) data and video imagery were collected to characterize trawlable and untrawlable areas and to ultimately improve efforts to determine habitat-specific groundfish biomass. We surveyed areas of the Gulf of Alaska (GOA) (20-500 m depth) aboard the NOAA ship Oscar Dyson during 2011, from the Islands of Four Mountains in the Aleutians to eastern Kodiak Island. Additional ME70 data were collected opportunistically during the winter 2012 acoustic trawl surveys. ME70 data were collected continuously along the ship trackline (1-20 nmi spacing) and at fine-scale survey locations in 2011 with 100% seafloor coverage (n = 21). Video data were collected at fine-scale survey sites using a drop camera (n = 47 stations). ME70 data were matched to the spatial location of previously conducted AFSC bottom-trawl survey hauls (n = 582) and 2011 camera stations to discriminate between trawlable and untrawlable seafloor types in the region of overlap between the haul or camera path and the ME70 data. Angle-dependent backscatter strength, backscatter mosaics, and other multibeam metrics were extracted from the ME70 data at these locations. Haul locations show separation in backscatter strength based on performance, previously classified as successful or unsuccessful due to gear damage from contact with the seafloor. Successful haul locations have values that correspond to finer grainsize, or the lack of untrawlable features such as boulders and rock. A similar pattern was observed for the camera stations characterized as trawlable or untrawlable from video. The best descriptors for seafloor trawlability will be identified among multibeam metrics to map the predicted trawlability of the ME70 survey footprint. Continued opportunistic collection of ME70 data during Oscar Dyson operations will help refine existing classifications of untrawlable and trawlable areas in the GOA

Assessing rockfish abundance in complex habitats using acoustics and cameras

Many species of rockfishes (Sebastes spp.) are difficult to assess using trawl surveys due to their propensity to aggregate near the seafloor in rocky high relief areas. A feasibility study was conducted during October 2009 in such an area south of Kodiak Island, AK, to evaluate the use of standard fisheries acoustic survey methods in conjunction with stereo‐video cameras for estimating the distribution and abundance of dusky and northern rockfishes. Uniformly spaced parallel transects were repeatedly surveyed using single beam echosounders over several days. A multibeam echosounder was used to characterize the seafloor as trawlable or untrawlable and these designations were corroborated by camera. Rockfish abundance was estimated using a combination of acoustic and camerameasurements. At least 80% of the rockfish detections were observed in untrawlable habitat areas, and within 2.0 m of the seafloor. Over half of the rockfish seen by the camera were within the acoustic dead zone. Repeat passes exhibited high precision and there was no significant difference in fish abundance or height off bottom between night and day. Future work is planned during summer 2011 to evaluate the feasibility of using these methods in broader areas and for other rockfishes in the Gulf of Alaska

Juvenile Pacific Herring (Clupea pallasi) and their interactions with ecosystem components in the Strait of Georgia, British Columbia

Pacific Herring (Clupea pallasi) are an important prey species for a variety of predators as well as important to First Nations communities and to the commercial fishing industry. The recruitment of Pacific Herring varies substantially on an annual basis and can represent a large proportion of the adult population biomass, adding uncertainty to population estimates. A leading indicator to forecast their recruitment prior to their harvest would be helpful to understand year class strength. British Columbia’s Strait of Georgia juvenile herring and nearshore pelagic ecosystem survey has collected data from ten core transects in September-October since 1992. This data may help improve the understanding of factors that influence herring recruitment and their availability to their predators, such as Chinook and Coho Salmon. An objective of this study was to update the survey time series of the relative biomass and abundance (and associated variance) of age-0 herring. Results indicate that age-0 herring abundance varies interannually with high abundances in recent, even years and there was an increasing trend in fish condition during 1997-2010. Preliminary results indicate age-0 herring biomass may be a leading indicator of recruitment to the adult herring spawning population and to Chinook Salmon survival. We also explore potential ecological and trophodynamic interactions between herring and ecosystem components, zooplankton abundance, and environmental variability. Investigating the dynamics of ecological linkages among pelagic species will improve our understanding of valuable species in BC’s marine ecosystems

Recommendations for quantifying and reducing uncertainty in climate projections of species distributions.

Projecting the future distributions of commercially and ecologically important species has become a critical approach for ecosystem managers to strategically anticipate change, but large uncertainties in projections limit climate adaptation planning. Although distribution projections are primarily used to understand the scope of potential change-rather than accurately predict specific outcomes-it is nonetheless essential to understand where and why projections can give implausible results and to identify which processes contribute to uncertainty. Here, we use a series of simulated species distributions, an ensemble of 252 species distribution models, and an ensemble of three regional ocean climate projections, to isolate the influences of uncertainty from earth system model spread and from ecological modeling. The simulations encompass marine species with different functional traits and ecological preferences to more broadly address resource manager and fishery stakeholder needs, and provide a simulated true state with which to evaluate projections. We present our results relative to the degree of environmental extrapolation from historical conditions, which helps facilitate interpretation by ecological modelers working in diverse systems. We found uncertainty associated with species distribution models can exceed uncertainty generated from diverging earth system models (up to 70% of total uncertainty by 2100), and that this result was consistent across species traits. Species distribution model uncertainty increased through time and was primarily related to the degree to which models extrapolated into novel environmental conditions but moderated by how well models captured the underlying dynamics driving species distributions. The predictive power of simulated species distribution models remained relatively high in the first 30 years of projections, in alignment with the time period in which stakeholders make strategic decisions based on climate information. By understanding sources of uncertainty, and how they change at different forecast horizons, we provide recommendations for projecting species distribution models under global climate change