IPHC oceanographic monitoring program 2013

Transcription

1 IPHC oceanographic monitoring program 2013 Lauri L. Sadorus and Jay Walker Abstract This was the fifth year the International Pacific Halibut Commission s (IPHC) comprehensive profiler project collected oceanographic data from southern Oregon northward to British Columbia, into the Gulf of Alaska, Bering Sea, and Aleutian Islands. In addition, 15 stations were added in northern California this year. The IPHC has been operating profilers since 2000 on a limited basis and coastwide since A total of 1,065 successful casts were made this year out of a possible 1,297. Background Since the expansion of its survey operations in 1997, the International Pacific Halibut Commission (IPHC) has annually conducted fishing operations at more than 1,000 stations ranging geographically from off the Oregon coast to the Bering Sea. Periodically, additional stations are added in areas not normally surveyed because of a particular question or concern. For example, in 2011, the Puget Sound was surveyed to ground truth predicted biomass in the area. This year, 15 stations were added in northern California due to a recently developed halibut sport fishery in the area. All survey stations are located on the continental shelf at depths of meters, on an equidistant 10-nmi grid (Henry et al. 2014). As such, the IPHC operates the largest consistent sampling program of any research agency in the north Pacific. Fundamental changes in the physical and chemical makeup of the ocean waters affect the health and distributions of organisms living there and this is an area of investigation that has gained momentum in recent years as scientists and stakeholders try to understand the direct and indirect effects on fisheries. Primary and secondary productivity are directly driven by variations in water temperature, salinity, dissolved oxygen, and other environmental factors. Acidification of the oceans and upwelling-induced hypoxia are two of the phenomena linked to global climate change in recent years. The oceans are predicted to become warmer, more oxygen deprived, and more acidic as a result of global climate change. Coupling oceanographic observations with catch estimates from the IPHC setline survey (Henry et al. 2014) over time is a necessary next step to understanding the impacts of these changing conditions on the halibut resource. In the late 1990s, the IPHC began considering the feasibility of collecting environmental data alongside halibut catch data on the setline survey. In 2000, a Sea-Bird Seacat SBE-19 water column profiler equipped with sensors to measure depth, temperature, and salinity was purchased by the IPHC and deployed aboard a longline vessel chartered for the annual setline survey. The profiler was then deployed on different vessels and in different areas successfully for several years. In 2005, a dissolved oxygen (DO) sensor was added to the profiler and proved well-suited for the project s purposes. In 2007, the IPHC received a grant from the Oregon Department of Fish and Wildlife Restoration and Enhancement Program to purchase a second Sea-Bird Seacat SBE- 19plus (an updated version of the SBE-19) dedicated to the IPHC survey stations off the Oregon coast. This new profiler was equipped with additional sensors to measure dissolved oxygen (SBE- 43), ph (SBE-18), and chlorophyll a concentration (WET Labs ECO-FLRTD). 325

2 The successful deployment of these two profilers aboard multiple vessels over multiple years and areas provided proof of concept that these oceanographic data could be collected with minimal disruption to the core survey operations. To that end, the IPHC received a grant from the National Oceanic and Atmospheric Administration (NOAA) in late The grant allowed for the purchase of 14 Sea-Bird Seacat SBE19plus V2 water column profilers, laptop computers for each, as well as annual maintenance and data processing costs for four years. The grant expired in September 2012 and maintenance costs are currently borne by the IPHC. Methods Instruments The Seacat profilers are equipped with a titanium housing which is rated for depths to 7,000 meters. The sensors have maximum depth ratings ranging from 1,000 m to 7,000 m, which is sufficient for all IPHC survey stations. The units weigh approximately 25 kg in air and 14 kg in water. The profiler is protected by a stainless steel cage, 96 cm tall and specially designed for each unit. Software for downloading and displaying the data is provided by the manufacturer. Communication between the profiler and the laptop computer is accomplished via USB ports. To adapt the profiler for deployment from a halibut fishing vessel, a system was designed using weights and floats that permits the profiler to descend rapidly enough through the water column to collect valid data and also ensures that the unit will not crash into or become permanently attached to the ocean bottom (Hare 2001). A sustained descent rate of 1-2 m/s is the target, and the weight of the assembly in the water is sufficient that, if the unit is allowed to free fall, the target descent rate is achieved. A 15-meter anchor line is attached to the bottom of the profiler cage using a section of gangion line as a weak link (in case the anchor cannot be freed from the bottom). A 40-pound longline anchor is attached to the end of the 15-meter line. To the top of the cage, two floats are attached that effectively offset the weight of the anchor in water. The floats are attached to standard halibut buoy line which is almost neutrally buoyant. Deployment A profiler unit was deployed at each station, just prior to hauling the fishing gear at that station. To deploy the unit, the anchor was lowered into the water followed by the profiler and cage, and then the buoy line and buoys. After a minimum 90-second acclimation period at the surface, the line was released, and the full setup allowed to free fall to the bottom. Each profiler took measurements from the surface to depth at a rate of four per second and a pump ensured consistent water flow past the sensors. Once the anchor hit the bottom, the remainder of the unit ceased descent shortly afterward, due to the strong positive buoyancy of the floats. On board the vessel, it was usually evident when the anchor hit bottom because of a noticeable slackening of the line. At that time, the vessel s gurdy was engaged and the profiler was immediately hauled back aboard. Once on deck, a series of protocols were executed to clean the sensors and store the unit until the next deployment, as outlined in IPHC (Unpub.). Data capture Each profiler was equipped with a dedicated laptop computer that accompanied it into the field. Approximately once a day, the profiler was connected to the computer, data were uploaded, 326

3 and the profiler unit was then reset for the next day s casts. The data were sent remotely or via data storage cards back to the Seattle office after each trip. To facilitate quicker retrieval and processing of the data in 2013, a cloud storage service called Cubby ( was used to transmit the data more efficiently to the IPHC office. When the vessels arrived in port after each trip, the samplers connected the laptops to the internet in order to sync the collected data to a secured storage location in the cloud. The IPHC office staff were then notified that the data were available for download. Results Data collection In 2013, a total of 11 fishing vessels were chartered to complete the IPHC setline survey (Henry et al. 2014) and each vessel was outfitted with a Seacat19plus V2 profiling unit, a laptop computer, and accessory gear. Out of a possible 1,297 stations coastwide, 1,065 yielded useable environmental data (Table 1), resulting in an 82% success rate. There were several reasons for unsuccessful data capture. The vessel captain and lead biologist together decide whether it is prudent to launch the profiler, given the conditions at each station. Poor weather and strong tides were the most common reasons given for aborted casts. On stations where tides were strong but the station was otherwise deemed viable, the samplers were allowed to incorporate an additional pound weight to the bottom of the assembly to achieve a more vertical descent. Mechanically, there were several reports of units shutting off mid-profile, resulting in unusable data. Changing batteries, tightening the magnetic switch, replacing profilerto-computer cables, and interfacing with the IPHC office to troubleshoot computer problems resulted in the majority of issues being corrected quickly. In one case, the profiler was pulled from the field and replaced as soon as possible. The ph sensor on two profilers malfunctioned while in the field and ph data were lost, although remaining sensor data were viable. Overall, this resulted in 960 useable stations of ph data. Two profilers were lost in previous years, but none have been lost since One laptop computer was damaged beyond repair in 2013, when it was unexpectedly swamped by saltwater while being carried across the deck. Otherwise, the use of the solid state drives that were added to the computers in 2012, the redundant backup methods, and streamlined data delivery to the office proved effective at protecting the computers from significant damage due to impacts and protecting the data from loss. Environmental conditions The sampled area encompasses a wide range of environmental conditions. Table 2 provides near-bottom ranges and averages for each parameter measured except chlorophyll which is reported at 25 m depth. The highest chlorophyll concentration was found east of Amchitka Pass in the Aleutian Islands, but there were blooms of primary production encountered coastwide. Coolest temperatures were found in the northern Bering Sea along the 4D Edge. The coldest station is routinely found off of St. Matthew Island and often has temperatures below 0 C. Unfortunately, a profiler malfunction resulted in those stations not being sampled in The warmest water was found in Hecate Strait, B.C., but there were also relatively warm temperatures in the western Gulf of Alaska (Figs. 1-5). The most acidic water was found off of Oregon and Washington in the upwelling zone, which was expected, but the values are lower than anticipated. Data presented in 327

4 this report are preliminary and it is possible that those values will be adjusted once analyzed and field calibrations are applied. Based on the first five years of this project, general environmental differences among the major areas of the coast have been identified. Relative to the other sampled areas, near-bottom conditions along the U.S. west coast and B.C. are characterized by low DO, low ph (more acidic water), warmer temperatures, and moderate amounts of primary production. Gulf shelf waters differ between east and west, with the western portion tending towards warmer temperatures, higher DO, and less acidic water than the eastern and central Gulf, especially around Kodiak Island and Cook Inlet. The Bering Sea and Aleutian Islands are characterized by cooler temperatures, higher DO except at very deep stations, moderate primary production, and a variety of ph conditions. Appendix I (available online only) provides a closer look at the conditions in each of these areas. Data processing and availability A primary goal of this project is to make the survey profiler data available to scientists worldwide. The IPHC is working with the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) at the University of Washington and NOAA s Pacific Marine Environmental Laboratory to process the oceanographic data and make them publicly accessible. The complete set of data is now available at: Processing of the 2012 and 2013 data is in progress. Acknowledgments The success of the profiler project depends on the efforts and cooperation of many people. We would like to acknowledge the IPHC survey program staff for competently incorporating the profiler project into the survey protocols, Andy Vatter for making sure the gear is ready for the field, IPHC sea samplers for their hard work and attention to detail in collecting the data, the survey vessel captains and crews for making sure the Seacats are safely retrieved after every cast, and Peggy Sullivan at NOAA/JISAO for her tireless work on the data and website. References Hare, S. H Deployment of a water column profiler from a halibut longliner during IPHC survey operations. Int. Pac. Halibut Comm. Report of Assessment and Research Activities 2000: Henry, E., Dykstra, C. L., Geernaert, T. O., Soderlund, E., and Ranta, A. M Standardized stock assessment survey. Int. Pac. Halibut Comm. Report of Assessment and Research Activities International Pacific Halibut Commission. Unpub. Oceanographic sampling on IPHC setline surveys, Seacat manual Operation manual. International Pacific Halibut Commission. 54 p. 328

5 Table 1. Number of profiler casts completed during the 2013 standardized stock assessment survey, by survey region and vessel. Stations Region Profiled Possible Vessel name N. California Pacific Surveyor Oregon Pacific Surveyor Washington Pacific Surveyor Vancouver Van Isle Goose Island Van Isle St. James Star Wars II Charlotte Star Wars II Ketchikan Pender Isle Ommaney Pender Isle Sitka Pender Isle Fairweather Bold Pursuit Yakutat Bold Pursuit Prince William Sound Bold Pursuit Seward Waterfall Gore Point Waterfall Portlock Clyde Albatross Waterfall Shelikof Clyde Trinity Free to Wander Semidi Free to Wander Chignik Free to Wander Shumagin La Porsche Sanak La Porsche Unalaska Kema Sue 4A Edge Kema Sue 4D Edge Kema Sue Adak Norcoaster Attu Norcoaster Total regions: 28 1,065 1,297 Total vessels:

6 Table 2. A summary of near-bottom coast-wide environmental conditions encountered during the survey in Average Std. dev. Min. Max. Depth (m) Temperature ( o C) Salinity (psu) DO (ml/l) ph Chlorophyll (mg/m 3 25 m depth

7 Figure 1. Coastwide near-bottom temperature ( C) as measured during the IPHC annual setline survey in Temperatures are depicted by colors defined on the bar to the right of the map. Note that the map should be viewed in color, available on the IPHC website: Figure 2. Coastwide near-bottom salinity (psu) as measured during the IPHC annual setline survey in Salinity is depicted by colors defined on the bar to the right of the map. Note that the map should be viewed in color, available on the IPHC website: 331

8 Figure 3. Coastwide near-bottom dissolved oxygen (ml/l) as measured during the IPHC annual setline survey in DO is depicted by colors defined on the bar to the right of the map. Note that the map should be viewed in color, available on the IPHC website: Figure 4. Coastwide near-bottom ph as measured during the IPHC annual setline survey in ph level is depicted by colors defined on the bar to the right of the map. Note that the map should be viewed in color, available on the IPHC website: 332

9 Figure 5. Coastwide chlorophyll concentration (mg/m 3 ) measured at 25 m depth during the IPHC annual setline survey in Chlorophyll level is depicted by colors defined on the bar to the right of the map. Note that the map should be viewed in color, available on the IPHC website: raras.html 333

10 Appendix (for website/full color viewing) The following is a series of plots produced using Ocean Data View (Schlitzer 2010) software illustrating oceanographic conditions in summer 2013 as measured by Sea-Bird profilers during the IPHC standardized setline survey. Appendix Figure 1 contains information for the west coast, Appendix Figure 2 for the Gulf of Alaska, and Appendix Figure 3 for the Bering Sea and Aleutian Islands. Temperature, salinity, dissolved oxygen, and ph are calculated using the deepest measurements at each station - typically 5-10 m off bottom. Chlorophyll a concentration is calculated using measurements at 25-m depth. The data are illustrated as iso-surface plots which is a continuous surface using the point values and interpolating between points. Survey stations (i.e. where measurements were actually taken) are denoted as black dots. Note that data are preliminary. Appendix Figure 1: U.S. West Coast and British Columbia Appendix Figure 2: Gulf of Alaska Appendix Figure 3: Bering Sea and Aleutian Islands To view the complete document including the full color maps, please visit the IPHC website: Reference Schlitzer, R., Ocean Data View, 334