uid=EDI,o=EDI,dc=edirepository,dc=org all https://orcid.org/0000-0003-3514-7996 all public read doi:10.6073/pasta/3a26cb75ad1707a1e8f7215ce626ab34 United States Fish and Wildlife Service Geoff Steinhart USFWS Habitat Restoration Coordinator geoffrey_steinhart@fws.gov https://www.fws.gov/office/lodi-fish-and-wildlife 0000-0003-3514-7996 Zachary Jackson USFWS Project Coordinator Zachary_Jackson@fws.gov 0000-0003-3048-2541 Program Founder Laura Heironimus Washington Department of Fish and Wildlife Biologist Laura.Heironimus@dfw.wa.gov Program Founder Alin González USFWS CVPIA Data Manager alin_gonzalezbarnes@fws.gov 0000-0003-4041-0496 CVPIA Data Manager 2024-01-23 Overview The Central Valley Project Improvement Act (CVPIA) funds habitat improvement work and associated monitoring in the Central Valley of California to increase salmonid populations in furtherance of meeting CVPIA fish doubling goals. This data package contains two datasets for White Sturgeon (Acipenser transmontanus) monitoring in the San Joaquin River (SJR) conducted by the US Fish and Wildlife Service, Lodi Fish and Wildlife Office. The objective of this sampling to was determine if White Sturgeon were spawning in the San Joaquin River and to explore where and when spawning occurred, within areas where adult White Sturgeon were known to congregate during the suspected spawning season. SJR_Egg_WST_Set Data This dataset contains data on egg mat sets used to document White Sturgeon spawning in the San Joaquin River. Sets were made at non-random locations from February to May in 2011-2018. In 2017, additional “blitz” sets were used in areas where eggs were detected. Details about set location, timing, and environmental conditions are included, along with the total number eggs of White Sturgeon and other non-sturgeon eggs. SJR_Egg_WST_Catch Data This dataset contains data specific to eggs found in egg mat nets in the San Joaquin River. Across all years, the diameter of eggs (or groups of eggs) were recorded. In 2011 and 2012, efforts were made to describe the developmental stage of White Sturgeon eggs and estimates of spawning timing were sometimes calculated. anadromous CVPIA San Joaquin River United States Fish and Wildlife Service USFWS white sturgeon aquatic ecosystems distribution ecology fishes freshwater monitoring rivers LTER Controlled Vocabulary This information is released under the Creative Commons license - Attribution - CC BY (https://creativecommons.org/licenses/by/4.0/). The consumer of these data ("Data User" herein) is required to cite it appropriately in any publication that results from its use. The Data User should realize that these data may be actively used by others for ongoing research and that coordination may be necessary to prevent duplicate publication. The Data User is urged to contact the authors of these data if any questions about methodology or results occur. Where appropriate, the Data User is encouraged to consider collaboration or co-authorship with the authors. The Data User should realize that misinterpretation of data may occur if used out of context of the original study. While substantial efforts are made to ensure the accuracy of data and associated documentation, complete accuracy of data sets cannot be guaranteed. All data are made available "as is." The Data User should be aware, however, that data are updated periodically and it is the responsibility of the Data User to check for new versions of the data. The data authors and the repository where these data were obtained shall not be liable for damages resulting from any use or misinterpretation of the data. Thank you. https://doi.org/10.6073/pasta/3a26cb75ad1707a1e8f7215ce626ab34 Lower San Joaquin River, California, USA. -121.24689 -121.12253 37.67302 37.54795 2011-04-18 2018-05-11 All fishes were identified to species when possible or, at a minimum, to family. Kingdom Metazoa metazoans 33208 Phylum Chordata chordates 7711 Subphylum Craniata 89593 Superclass Actinopterygii ray-finned fishes 7898 Class Actinopteri 186623 Subclass Chondrostei 32440 Order Acipenseriformes sturgeons and paddlefish 7899 Suborder Acipenseroidei 186622 Family Acipenseridae sturgeons 7900 Subfamily Acipenserinae 124129 Genus Acipenser 7901 Sampling has concluded for the juvenile sturgeon sampling. This package contains all the relevant data. We do not plan on updating this package in the future. notPlanned Kristie Braken-Guelke USFWS Biological Technician Crew Lead kristie_braken-guelke@fws.gov https://www.fws.gov/office/lodi-fish-and-wildlife Paul Cadrett USFWS Habitat Restoration Coordinator paul_cadrett@fws.gov https://www.fws.gov/office/lodi-fish-and-wildlife 0000-0002-6312-0507 Environmental Data Initiative info@edirepository.org https://edirepository.org 0330j0z60 Environmental Data Initiative Study Area The San Joaquin River originates from the central Sierra Nevada and drains parts of the Sierra Nevada and Diablo mountain ranges. It flows 531 km, first west towards the floor of the Central Valley of California, then north towards the Sacramento-San Joaquin Delta, eventually reaching the Pacific Ocean. Friant Dam (river km [rkm] 431), forms a complete barrier to upstream anadromous fish passage. Downstream of Friant Dam, the river encounters increasingly greater anthropogenic influence through water diversions and habitat alteration. Sampling for White Sturgeon (Acipenser transmontanus) occurred at various locations in a 24-km reach of the San Joaquin River from Sturgeon Bend (rkm 119) to Grayson Road Bridge (rkm 143). Field and Lab Methods Sturgeon eggs were sampled by deploying artificial substrate samplers (i.e., egg mats) in close proximity to presumed spawning areas based on hydraulic conditions, side-scan sonar images, and angler and warden observations. Egg mats were constructed from two 89 x 65-cm rectangular sections of furnace filter material secured back-to-back within a welded steel framework (McCabe and Beckman 1990; Schaffter 1997; Poytress et al. 2009). The orientation of the furnace filter material allowed either side of the egg mat to collect eggs. Egg mats were held in position by a 2.0-kg anchor attached to the upstream end of the egg mat with two 76-cm lengths of 9.5-mm diameter braided polypropylene rope. A labeled float was attached to the downstream end of each egg mat with a 9.5-mm diameter braided polypropylene rope. Float line length varied between egg mats, depending on water depth and velocity. Mats were predominantly deployed in areas of accelerating velocities (i.e., areas flanking deepest portions of pools) and were set in pairs. Sampling occurred within February to June 2011-2018, but the exact sampling dates and range varied by year. Environmental and sample effort data were collected in conjunction with egg mat sampling. Sample effort data consisted of the date and time individual egg mats were set and retrieved. In 2011, environmental data collected at mat set and retrieval included water depth (m), latitude, and longitude. Turbidity was measured only at mat set in 2011. Starting in 2012, environmental data consisted of water depth, latitude and longitude, water temperature, turbidity, and weather at both mat set and mat retrieval. Depth (m), temperature (°C), and coordinates were recorded directly above each egg mat. Turbidity (nephelometric turbidity units, NTUs) was measured with a Hach turbidimeter (Model 2100P). In addition, beginning in 2012, hourly water temperature was monitored at egg mat with a temperature logger (logger data not included in this data package). Beginning in May 2014, habitat (i.e., eddy, pool, or run) at each deployment site was also recorded. Egg mat sampling consisted of visual inspection after retrieval, generally twice per week throughout the sample period. Egg mats were pulled from the river, placed on the deck of a boat in a custom-made egg mat carrier, and inspected on both sides by at least two field crew members. After initial inspection, egg mats were rinsed with water to remove debris and sediment and then re-inspected. Rinse water and debris were filtered by a removable 3.2-mm mesh net placed within the egg mat carrier below each egg mat to capture any dislodged eggs. After the second egg mat inspection and after checking the mesh nets, mats were redeployed. All eggs removed from mats were counted and identified to species in the field with an egg key (Reyes et al. 2007; Wang 2010; Reyes 2011). All suspected sturgeon eggs and unidentified eggs were placed into vials of 95% ethyl alcohol (EtOH) for laboratory identification and further analysis. Suspected sturgeon eggs were sent to the University of California-Davis (UCD) for species confirmation, photography, measurement of egg diameter, and determination of developmental stage (Dettlaff et al. 1993). Egg length and width were measured with an Olympus dissecting microscope with a camera lucida and a Nikon Microplane II digital image analyzing tablet. In 2011 and 2012, estimates of date and time of fertilization (i.e., spawn timing) were estimated based on an average water temperature, egg developmental stage, and embryonic development rates for White Sturgeon (Wang et al. 1985, 1987). Data Management Data were recorded on paper datasheets in the field or lab and later entered into Excel spreadsheets. After entry, electronic data were reviewed and compared with paper datasheets for accuracy. In addition, during the preparation of the included data files, environmental variable values were checked for odd or impossible values (e.g., dissolved oxygen values exceeding 20 mg/l). All coordinates were mapped to identify location errors that did not fall within the river channel. Data points that were identified as errors were again compared to the original paper datasheets and corrected or, if the correction was not apparent, the erroneous data were removed, but the rest of the data for that set (or egg) was left in place. Additional year-specific information is available from annual reports published on this work (Gruber et al. 2012, Jackson and VanEenennaam 2013, Faukner et al. 2014, Faukner et al. 2015). References Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. Faukner, J. R., and Z. J. Jackson. 2014. 2013 San Joaquin River sturgeon spawning survey. Stockton Fish and Wildlife Office, Anadromous Fish Restoration Program, U. S. Fish and Wildlife Service, Lodi, California. Faukner, J. R., S. V. Rayford, L. B. Heironimus, and Z. J. Jackson. 2015. 2014 San Joaquin River sturgeon spawning survey. Lodi Fish and Wildlife Office, Anadromous Fish Restoration Program, U.S. Fish and Wildlife Service, Lodi, California. Gruber, J. J., Z. J. Jackson, and J. P. Van Eenennaam. 2012. 2011 San Joaquin River sturgeon spawning survey. Lodi Fish and Wildlife Office, Anadromous Fish Restoration Program, U. S. Fish and Wildlife Service, Stockton, California. Jackson, Z. J., and J. P. Van Eenennaam. 2013. 2012 San Joaquin River sturgeon spawning survey. Stockton Fish and Wildlife Office, Anadromous Fish Restoration Program, U.S. Fish and Wildlife Service, Lodi, California. McCabe, G. T., and L. G. Beckman. 1990. Use of an artificial substrate to collect white sturgeon eggs. California Department of Fish and Game 76(4):248–250. Poytress, W. R., J. J. Gruber, D. A. Trachtenbarg, and J. P. Van Eenennaam. 2009. 2008 upper Sacramento River green sturgeon spawning habitat and larval migration surveys. Annual Report of U.S. Fish and Wildlife Service to US Bureau of Reclamation, Red Bluff, California. Schaffter, R. G. 1997. White sturgeon spawning migrations and location of spawning habitat in the Sacramento River, California. California Fish and Game 83:1–20. Reyes, R. C., B. W. Bird, and P. F. Raquel. 2007. Guide to the fishes of the Tracy Fish Collection Facility. U.S. Department of Interior, Bureau of Reclamation, Tracy Series Volume 36. Reyes, R. C. 2011. Dichotomous key to fish eggs of the Sacramento-San Joaquin river delta. U.S. Department of Interior, Bureau of Reclamation, Tracy Technical Bulletin 2011-1. Wang, Y. L., F. P. Binkowski, and S. I. Doroshov. 1985. Effect of temperature on early development of white and lake sturgeon, Acipenser transmontanus and A. fulvescens. Environmental Biology of Fishes 14:43–50. Wang, Y. L., R. K. Buddington, and S. I. Doroshov. 1987. Influence of temperature on yolk utilization by the white sturgeon, Acipenser transmontanus. Journal of Fish Biology 30:263–271. Wang, J. C. S. 2010. Fishes of the Sacramento-San Joaquin river delta and adjacent waters, California: a guide to early life histories. U.S. Department of Interior, Bureau of Reclamation, Tracy Series Volume 44 Special Publication. United States Fish and Wildlife Service Creator Overview The Central Valley Project Improvement Act (CVPIA) funds habitat improvement work and associated monitoring in the Central Valley of California to increase salmonid populations in furtherance of meeting CVPIA fish doubling goals. This data package contains two datasets for White Sturgeon (Acipenser transmontanus) monitoring in the San Joaquin River (SJR) conducted by the US Fish and Wildlife Service, Lodi Fish and Wildlife Office. The objective of this sampling to was determine if White Sturgeon were spawning in the San Joaquin River and to explore where and when spawning occurred, within areas where adult White Sturgeon were known to congregate during the suspected spawning season. SJR_Egg_WST_Set Data This dataset contains data on egg mat sets used to document White Sturgeon spawning in the San Joaquin River. Sets were made at non-random locations from February to May in 2011-2018. In 2017, additional “blitz” sets were used in areas where eggs were detected. Details about set location, timing, and environmental conditions are included, along with the total number eggs of White Sturgeon and other non-sturgeon eggs. SJR_Egg_WST_Catch Data This dataset contains data specific to eggs found in egg mat nets in the San Joaquin River. Across all years, the diameter of eggs (or groups of eggs) were recorded. In 2011 and 2012, efforts were made to describe the developmental stage of White Sturgeon eggs and estimates of spawning timing were sometimes calculated. U.S. Bureau of Reclamation United States Fish and Wildlife Service Creator Overview The Central Valley Project Improvement Act (CVPIA) funds habitat improvement work and associated monitoring in the Central Valley of California to increase salmonid populations in furtherance of meeting CVPIA fish doubling goals. This data package contains three datasets for adult White Sturgeon (Acipenser transmontanus) monitoring in the San Joaquin River (SJR) conducted by the US Fish and Wildlife Service, Lodi Fish and Wildlife Office. The primary purpose for this sampling was to capture White Sturgeon and implant acoustic telemetry tags for a tracking project. Therefore, the data are useful for determining when and where White Sturgeon were captured, but they should not be used to determine actual distribution or abundance. SJR_Adult_WST_Set Data This dataset contains data from a sampling program using various methods to catch adult White Sturgeon in the San Joaquin River. Sets were made at targeted locations primarily from March-May in 2012-2018 (other dates were occasionally sampled). SJR_Adult_WST_Catch Data This dataset contains data for individual fish caught via gillnets, trammel nets, setlines, or angling in the San Joaquin River. Species and fork length were recorded for all fish. For White Sturgeon, girth, maturation, tag, and surgery information are provided. SJR_Fish_Taxonomy Data This dataset contains data for fish codes used in the Catch datafile. For each species that was captured, the Species codes are listed with the corresponding Interagency Ecological Program code, common name, taxonomy (Phylum, Class, Order, Family, Genus, and Species), and whether or not the species is native to the region. U.S. Bureau of Reclamation United States Fish and Wildlife Service Creator Overview The Central Valley Project Improvement Act (CVPIA) funds habitat improvement work and associated monitoring in the Central Valley of California to increase salmonid populations in furtherance of meeting CVPIA fish doubling goals. This data package contains three datasets for juvenile White Sturgeon (Acipenser transmontanus) monitoring in the San Joaquin River (SJR) conducted by the US Fish and Wildlife Service, Lodi Fish and Wildlife Office. After two years of this experimental sampling program, it was discontinued due to low catches of White Sturgeon. SJR_Juvenile_WST_Set Data This dataset contains data on an experimental sampling program using trammel nets and setlines to catch juvenile White Sturgeon in the San Joaquin River. Sets were made at targeted locations from November-January in 2016 and 2017. One White Sturgeon (1000 mm fork length) was captured in a trammel net in 2016. SJR_Juvenile_WST_Catch Data This dataset contains data for individual fish caught in trammel nets or setlines in the San Joaquin River. Species and fork length were recorded for all fish. For White Sturgeon, girth, maturation, and tag information are provided. SJR_Fish_Taxonomy Data This dataset contains data for fish codes used in the Catch datafile. For each species that was captured, the Species codes are listed with the corresponding Interagency Ecological Program code, common name, taxonomy (Phylum, Class, Order, Family, Genus, and Species), and whether or not the species is native to the region. U.S. Bureau of Reclamation United States Fish and Wildlife Service Creator Overview The Central Valley Project Improvement Act (CVPIA) funds habitat improvement work and associated monitoring in the Central Valley of California to increase salmonid populations in furtherance of meeting CVPIA fish doubling goals. This data package contains three datasets for larval White Sturgeon (Acipenser transmontanus) monitoring in the San Joaquin River (SJR) conducted by the US Fish and Wildlife Service, Lodi Fish and Wildlife Office. SJR_Larval_WST_Set Data This dataset contains data on an experimental sampling program using boat-mounted drift nets (D-frame nets), a large drift net attached to a stationary pontoon (pontoon net), and otter trawls to catch larval White Sturgeon in the San Joaquin River. Sets were made at targeted locations from March-July in 2013, 2015, 2016, and 2017. A total of ten White Sturgeon were captured in 2016 and 11 in 2017, all with D-frame driftnets. SJR_Larval_WST_Catch Data This dataset contains data for individual fish caught in the San Joaquin River. Species and fork length were recorded for most individuals. SJR_Fish_Taxonomy Data This dataset contains data for fish codes used in the Catch datafile. For each species that was captured, the Species codes are listed with the corresponding Interagency Ecological Program code, common name, taxonomy (Phylum, Class, Order, Family, Genus, and Species), and whether or not the species is native to the region. U.S. Bureau of Reclamation SJR_Egg_WST_Set This dataset contains data on egg mat sets used to document White Sturgeon spawning in the San Joaquin River. Sets were made at non-random locations from February to May in 2011-2018. In 2017, additional “blitz” sets were used in areas where eggs were detected. Details about set location, timing, and environmental conditions are included, along with the total number eggs of White Sturgeon and other non-sturgeon eggs. SJR_Egg_WST_Set.csv 270835 af7f052f0a50f9eb96785c3b68874c2d 1 \r\n column , " https://pasta.lternet.edu/package/data/eml/edi/1564/1/6b5f8484d49ad282585406a695e75a20 SetID SetID Assigned set identification number to link set data to catch data. SetIDs were generated using the date of mat set and the float number for the set (YYYY_MM_DD_FloatNumber). string text StationCode StationCode Colloquial name assigned to set location. string text FloatNumber FloatNumber Number on the float used to mark the egg mat set. string text DateStart DateStart Date (YYYY-MM-DD) the gear was set. dateTime YYYY-MM-DD DateEnd DateEnd Date (YYYY-MM-DD) the gear was retrieved. dateTime YYYY-MM-DD TimeStart TimeStart Time (HH:MM, 24 hr) the gear was set. dateTime hh:mm TimeEnd TimeEnd Time (hh:mm, 24 hr) the gear was retrieved. dateTime hh:mm LatitudeStart LatitudeStart Latitude (DD.DDDDD°) at the location where the gear was set. float degree real NA Data not collected LongitudeStart LongitudeStart Longitude (DDD.DDDDD°) at the location where the gear was set. float degree real NA Data not collected LatitudeEnd LatitudeEnd Latitude (DD.DDDDD°) at the location where the gear was retrieved. float degree real NA Data not collected LongitudeEnd LongitudeEnd Longitude (DDD.DDDDD°) at the location where the gear was retrieved. float degree real NA Data not collected WeatherStart WeatherStart Weather conditions when the gear was set. string Clear Majority direct sunlight at start of sampling Cloudy Majority cloud cover at time of sampling Rain Rain at time of sampling WeatherEnd WeatherEnd Weather conditions when the gear was retrieved. string Clear Majority direct sunlight at time of sampling Cloudy Majority cloud cover at time of sampling Fog Fog at time of sampling Rain Rain at time of sampling DepthStart DepthStart Water depth (m) where the gear was set. float meter real NA Data not collected DepthEnd DepthEnd Water depth (m) where the gear was retrieved. float meter real NA Data not collected Habitat Habitat General river habitat type at location of set. string Eddy Set made in an eddy in the river Pool Set made in a pool in the river Run Set made in a run in the river TurbidityStart TurbidityStart Surface turbidity (NTU) when gear was set. float nephelometricTurbidityUnit real NA Data not collected TurbidityEnd TurbidityEnd Surface turbidity (NTU) when the gear was retrieved. float nephelometricTurbidityUnit real NA Data not collected TemperatureStart TemperatureStart Surface water temperature (°C) when gear was set. float celsius real NA Data not collected TemperatureEnd TemperatureEnd Surface water temperature (°C) when gear was retrieved. float celsius real NA Data not collected NumberWST NumberWST Number of White Sturgeon caught. float dimensionless real NA Data not collected NumberOther NumberOther Number of non-White Sturgeon caught. float dimensionless real NA Data not collected Comments Comments Comments about the site, set, or retrieval. string text no 1676 SJR_Egg_WST_Catch This dataset contains data specific to eggs found in egg mat nets in the San Joaquin River. Across all years, the diameter of eggs (or groups of eggs) were recorded. In 2011 and 2012, efforts were made to describe the developmental stage of White Sturgeon eggs and estimates of spawning timing were sometimes calculated. SJR_Egg_WST_Catch.csv 20479 2d9bb6d334ab52cf0827cb30a3f25e78 1 \r\n column , " https://pasta.lternet.edu/package/data/eml/edi/1564/1/4d17b79e4096e79c42ae5fc5deaa8728 SetID SetID Assigned set identification number to link set data to catch data. SetIDs were generated using the date of mat set and the float number for the set (YYYY_MM_DD_FloatNumber). string text EggDiam1 EggDiam1 Diameter, in mm, across the egg, orthogonal to EggDiam2 float millimeter real NA Data not collected EggDiam2 EggDiam2 Diameter, in mm, across the egg, orthogonal to EggDiam1 float millimeter real NA Data not collected Stage Stage Developmental stage of sturgeon eggs determined based on Dettlaff et al. (1993) string 4 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 9 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 10 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 11 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 14 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 18 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 19 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 22 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 26 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 27 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. 28 Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. NA Stage determined for this egg based on Dettlaff, T. A., A. S. Ginsburg, and O. I. Schmalhausen. 1993. Sturgeon fishes: developmental biology and aquaculture. Springer-Verlag, New York. NA Data not collected EstSpawnDate EstSpawnDate Estimated spawn date for sturgeon eggs based on Deng et al. (2002), Wang et al. (1985), and Wang et al. (1987) dateTime YYYY-MM-DD Viable Viable Describes whether the egg appeared viable or alive (Y) versus dead (N) upon capture. string N No, egg condition determined to be inviable Y Yes, egg condition determined to be viable NumberWST NumberWST Number of White Sturgeon eggs. float dimensionless real NA Data not collected NumberOther NumberOther Number of non-White Sturgeon eggs. float dimensionless real NA Data not collected Comments Comments Comments about the individual eggs or fish string text no 377 NTU- ratio of the amount of light transmitted through a water sample with the amount scattered at an angle of 90 degrees to one side Number of individual fish