Documenting fishes in an inland sea with citizen scientist diver surveys: using taxonomic expertise to inform the observation potential of fish species.

Long-term monitoring enables scientists and managers to track changes in the temporal and spatial distributions of fishes. Given the anthropogenic stressors affecting marine ecosystem health, there is a critical need for robust, comprehensive fish monitoring programs. Citizen science can serve as a meaningful, cost-effective strategy to survey fish communities. We compared data from 13,000 surveys collected over 21 years (1998-2019) by Reef Environmental Education Foundation (REEF) volunteer divers to a published compilation of Salish Sea ichthyofauna collected using an assortment of methods. Volunteer divers observed 138 of 261 recognized species in the Salish Sea, expanded the range of 18 species into additional Salish Sea sub-basins, and identified one species novel to the Salish Sea (Gibbonsia metzi - Striped Kelpfish). To identify Salish Sea fish species that are most suitable to be monitored by underwater visual census and to evaluate confidence in in situ identification, we developed a categorization system based on the likelihood of recreational divers and snorkelers encountering a given species, and on whether identification required a specimen in hand or could be classified to species visually (with or without a high-quality photograph). REEF divers encountered 62% (138 of 223) of the visually detectable species occurring in the region and 85% (102 of 120) of species most likely to be observed by recreational divers. Our findings show that citizen scientists provide valuable monitoring data for over half of the 261 marine and anadromous fish species known to occupy the Salish Sea, many of which are not routinely monitored otherwise.

Introduction

Comprehensive monitoring efforts are integral to marine ecosystem management and to predicting and mitigating the effects of anthropogenic change on marine biodiversity. Traditionally, fish occupancy is determined using a combination of fishery-dependent (i.e., catch data) and fishery-independent (e.g., remote underwater video, satellite imagery, hydroacoustics, visual transects, point-count surveys, roving diver surveys) monitoring (Murphy & Jenkins, 2010). The efficacy of a given monitoring technique depends on the target species and its unique characteristics, including size, behavior, crypticity, swimming speed, preferred habitat, and position in the water column (Holt et al., 2013; Harmelin-Vivien & Francour, 1992). Additionally, as observational methods vary in cost, invasiveness, and ease, choosing the appropriate monitoring tool depends on budgets and specific objectives of managers or researchers. It is useful to assess the benefits and disadvantages of different techniques to identify combinations that can maximize surveillance of target species, communities, or habitats while adhering to financial and other constraints.

Underwater visual census (UVC) is a minimally invasive, fishery-independent method in which snorkel or SCUBA is used to assess biodiversity and/or biomass in marine habitats (Pattengill-Semmens & Semmens, 2003). The roving diver technique (RDT; Schmitt & Sullivan, 1996) is a type of UVC especially suited for detecting shy, cryptic, or demersal fishes difficult to assess with other monitoring tools (Murphy & Jenkins, 2010). During RDT surveys, divers swim freely throughout a dive site while recording each observed fish species and a corresponding log-scale categorical abundance. The method can be conducted in a variety of habitats in depths up to 30 m (and beyond with specialized gear). As such, RDT is valuable for assessing frequencies of occurrence, spatial distributions, abundance estimates, and information on status and trends for a broad array of species. Data collected with other visual methods, such as belt transects, can be combined with RDT data to provide a holistic picture that includes species densities and size distributions (Holt et al., 2013).

Across the globe, citizen science programs train recreational divers to effectively monitor marine fishes, invertebrates, and algae (Branchini et al., 2015; Cerrano et al., 2016). The Reef Environmental Education Foundation (REEF) Volunteer Fish Survey Project trains volunteer divers and snorkelers to independently conduct RDT surveys, creating a system by which thousands of standardized surveys are conducted annually and recorded in a publicly accessible database (Pattengill-Semmens & Semmens, 2003). Within such a large pool of trained volunteers lies the potential for scientists and managers to increase their census capabilities by alleviating constraints on equipment, personnel, time, and accessibility to certain areas or habitats. Since 1993, the REEF Volunteer Fish Survey Project has been used worldwide to assess biodiversity and advance the conservation of threatened fishes and invertebrates, both alone and in combination with professional research efforts (Holt et al., 2013; Thorson et al., 2014). Data collected by REEF surveyors have informed numerous conservation and management efforts, including to detect and remove invasive species (Smith et al., 2017), discover new species (Allen et al., 2020), contribute to the recovery of threatened species (Tolimieri et al., 2017), document the impact of human population density on fish communities (Stallings, 2009), and trace the impacts of enigmatic marine diseases (Harvell et al., 2019).

To determine if RDT is an appropriate monitoring tool for a fish species, multiple factors surrounding the species of interest must be considered. This includes, but is not limited to, whether the species occurs at recreational diving depths, is cryptic or conspicuous, and if it can be discerned from closely related species without a specimen in hand (e.g., for meristic counts). Identifying the species that volunteers can potentially encounter and visually identify can improve the interpretation of data provided by this no-cost, high-value monitoring tool (Schmitt & Sullivan, 1996).

The Salish Sea is a 16,925 km2 inland sea bordered by Washington, USA, and British Columbia, Canada. In 2019, relying on preserved specimens in archival institutions, published records, and, especially for within-basin distributions, unpublished field notes and logbooks, Pietsch and Orr (2019) published species accounts for 260 fish species found in the Salish Sea, including distributions across sub-basins. As many of these taxonomic records were generated over a century ago, this compilation focused on providing a comprehensive, cumulative registry of Salish Sea ichthyofauna in addition to a current picture of biodiversity. Records were based on collections of specimens using an array of gear and techniques, including beach and purse seines, trawls, gillnets, traps, spearfishing, hook and lines, poisoning, stomach contents, and beach casts (e.g., Miller & Borton, 1980). Data from RDT or other visual surveys were not included. This compilation provides the best available baseline of the total fish that use, or have used, the Salish Sea ecosystem. While no one method will be suitable to capture all species, individual techniques such as RDT can be evaluated against this list to elucidate the scope of the survey tool.

Since 1998, REEF divers have conducted RDT surveys in the Salish Sea. We compiled REEF RDT surveys recorded over a span of 21 years (1998–2019) and compared these data to the Pietsch and Orr (2019) records of 260 Salish Sea fish species. Because relatively few specimens are collected and preserved from rocky reefs and rock walls (Pietsch & Orr, 2019), often a focus area for recreational divers, we hypothesized that observations by REEF surveyors would expand the geographic range and number of species documented in the Salish Sea based on Pietsch and Orr (2019). Certain fish species are inherently better suited than others for identification by RDT. Therefore, to identify Salish Sea fish species that can be monitored by REEF divers, we developed a categorization system based on the potential for recreational divers and snorkelers to encounter them, and on whether they can be visually identified to species with or without a high-quality photograph if encountered (i.e., a specimen in hand is not required for identification).

Methods

REEF Volunteer Fish Survey Project

We compiled REEF RDT survey data collected by volunteer divers in the Salish Sea from 1998 to 2019 (REEF, 2020). REEF divers record fish species sightings on preprinted data sheets and enter the data online (or, prior to 2007, mailed in optical scan forms). General data for each survey includes surveyor ID, surveyor experience level (expert or novice), geographic location, survey date, and a variety of environmental variables (e.g., habitat, depth, and visibility). Fish species sighted are recorded on a checklist, and for each, abundance is noted by one of four log-scale abundance index categories: “Single” (1 individual), “Few” (2–10 individuals), “Many” (11–100 individuals), or “Abundant” (> 100 individuals). After performing quality control (Pattengill-Semmens & Semmens, 2003), REEF staff transfer the data into a publicly accessible database (www.REEF.org). REEF categorizes surveyors as expert or novice based on their experience level and performance on a series of fish identification examinations. For this study, we included only surveys collected by expert surveyors. We excluded sightings of fishes identified to genus but not to species.

REEF vs. Pietsch and Orr comparison

The coordinates for each REEF survey location were used to group surveys into one of six oceanographic sub-basins of the Salish Sea: Central Basin (CB), Hood Canal (HC), Northern Straits (NS), South Puget Sound (SPS), Strait of Georgia (SOG), or Whidbey Basin (WB) (Moore et al., 2008; Thomson, 1994; Supplementary Map). We adapted the eight regions identified by Pietsch and Orr (2019) to these six sub-basins. A sub-basin was considered occupied by a given species if at least one expert-level REEF surveyor recorded the species there. Our list of REEF records in Table 1 is therefore a record of presence at any point in time between 1998 and 2019.

Table 1

Orders, families, and common and scientific names of fish species recorded in sub-basins of the Salish Sea, Strait of Georgia (SOG), Northern Straits (NS), Whidbey Basin (WB), Central Basin (CB), Hood Canal (HC), and South Puget Sound (SPS), by Reef Environmental Education Foundation (REEF) expert-level volunteer divers and by Pietsch and Orr (2019). Pietsch and Orr is designated by “PO.” An “X” indicates presence in a sub-basin; “#” indicates presence where REEF sightings expanded the known range of a species to another sub-basin within the Salish Sea. The identification category of each species describing its detectability in situ, as well as its sub-category (a–c) as per the identification key used in this study, is indicated by “ID”

Order	Family	Scientific name	Common name	CB		HC		NS		SOG		SPS		WB		ID
				REEF	PO	REEF	PO	REEF	PO	REEF	PO	REEF	PO	REEF	PO
Acipenseriformes	Acipenseridae	Acipenser medirostris	Green Sturgeon						X		X					2a
Acipenseriformes	Acipenseridae	Acipenser transmontanus	White Sturgeon	X	X		X		X		X		X		X	1a
Anguilliformes	Nemichthyidae	Nemichthys scolopaceus	Slender Snipe Eel		X				X		X				X	2a
Argentiniformes	Bathylagidae	Leuroglossus schmidti	Northern Smoothtongue								X					2a
Atheriniformes	Atherinopsidae	Atherinops affinis	Topsmelt						X							1a
Aulopiformes	Alepisauridae	Alepisaurus ferox	Longnose Lancetfish		X				X		X		X		X	2a
Aulopiformes	Paralepididae	Arctozenus risso	White Barracudina		X								X		X	2a
Aulopiformes	Synodontidae	Synodus lucioceps	California Lizardfish		X				X				X		X	2a
Batrachoidiformes	Batrachoididae	Porichthys notatus	Plainfin Midshipman	X	X	X	X	X	X	X	X	X	X	X	X	1a
Beloniformes	Scomberesocidae	Cololabis saira	Pacific Saury		X				X						X	2a
Carcharhiniformes	Carcharhinidae	Prionace glauca	Blue Shark		X										X	1a
Carcharhiniformes	Scyliorhinidae	Apristurus brunneus	Brown Cat Shark		X		X		X		X		X		X	2a
Carcharhiniformes	Triakidae	Triakis semifasciata	Leopard Shark						X							1a
Chimaeriformes	Chimaeridae	Hydrolagus colliei	Spotted Ratfish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Clupeiformes	Clupeidae	Alosa sapidissima	American Shad		X		X		X		X		X		X	2b
Clupeiformes	Clupeidae	Clupea pallasii	Pacific Herring	X	X	X	X	X	X	X	X	X	X	X	X	1a
Clupeiformes	Clupeidae	Sardinops sagax	Pacific Sardine		X		X	X	X	X	X		X		X	2a
Clupeiformes	Engraulidae	Engraulis mordax	Northern Anchovy	X	X	X	X	X	X	X	X	X	X		X	1a
Cottiformes	Pholidae	Apodichthys flavidus	Penpoint Gunnel	X	X	X	X	X	X	X	X	X	X	X	X	2c
Cottiformes	Agonidae	Agonopsis vulsa	Northern Spearnose Poacher	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Agonidae	Anoplagonus inermis	Smooth Alligatorfish	X	X			X	X	X	X			X	X	1a
Cottiformes	Agonidae	Bathyagonus alascanus	Gray Starsnout		X				X		X		X		X	2b
Cottiformes	Agonidae	Bathyagonus infraspinatus	Spinycheek Starsnout		X		X		X		X				X	2b
Cottiformes	Agonidae	Bathyagonus nigripinnis	Blackfin Poacher		X		X		X		X				X	2b
Cottiformes	Agonidae	Bathyagonus pentacanthus	Bigeye Poacher	X	X				X		X		X	X	X	2b
Cottiformes	Agonidae	Bothragonus swanii	Rockhead		X			X	X						X	1a
Cottiformes	Agonidae	Chesnonia verrucosa	Warty Poacher		X				X						X	1b
Cottiformes	Agonidae	Hypsagonus mozinoi	Kelp Poacher						X							1b
Cottiformes	Agonidae	Hypsagonus quadricornis	Fourhorn Poacher		X				X						X	1a
Cottiformes	Agonidae	Odontopyxis trispinosa	Pygmy Poacher	X	X	X	X	X	X	X	X	X	X	X	X	1b
Cottiformes	Agonidae	Pallasina aixa	Southern Tubenose Poacher		X			X	X	X	X				X	1b
Cottiformes	Agonidae	Podothecus accipenserinus	Sturgeon Poacher	X	X	X	X	X	X	X	X	X	X	X	X	1b
Cottiformes	Agonidae	Stellerina xyosterna	Pricklebreast Poacher						X							3a
Cottiformes	Agonidae	Xeneretmus latifrons	Blacktip Poacher	X	X	X	X		X		X		X	X	X	1b
Cottiformes	Agonidae	Xeneretmus leiops	Smootheye Poacher						X							3a
Cottiformes	Agonidae	Xeneretmus triacanthus	Bluespotted Poacher		X		X		X				X		X	2b
Cottiformes	Anarhichadidae	Anarrhichthys ocellatus	Wolf-eel	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Anoplopomatidae	Anoplopoma fimbria	Sablefish		X		X		X		X		X		X	2a
Cottiformes	Bathymasteridae	Ronquilus jordani	Northern Ronquil	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Cottidae	Artedius fenestralis	Padded Sculpin	X	X	X	X	X	X	X	X	X	X	X	X	2c
Cottiformes	Cottidae	Artedius harringtoni	Scalyhead Sculpin	X	X	X	X	X	X	X	X	X	X	X	X	1b
Cottiformes	Cottidae	Artedius lateralis	Smoothhead Sculpin	X	X	X	X	X	X	X	X	X	X	X	X	1b
Cottiformes	Cottidae	Artedius notospilotus	Bonehead Sculpin		X										X	3a
Cottiformes	Cottidae	Ascelichthys rhodorus	Rosylip Sculpin		X			X	X	X	X		X		X	1a
Cottiformes	Cottidae	Asemichthys taylori	Spinynose Sculpin	#		#		X	X	X	X	#		#		2c
Cottiformes	Cottidae	Chitonotus pugetensis	Roughback Sculpin	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Cottidae	Clinocottus acuticeps	Sharpnose Sculpin		X		X	X	X	X	X	X	X		X	2c
Cottiformes	Cottidae	Clinocottus embryum	Calico Sculpin		X				X		X		X		X	2b
Cottiformes	Cottidae	Clinocottus globiceps	Mosshead Sculpin		X				X						X	2b
Cottiformes	Cottidae	Cottus aleuticus	Coastrange Sculpin		X		X		X		X		X		X	2b
Cottiformes	Cottidae	Cottus asper	Prickly Sculpin		X		X		X		X		X		X	2b
Cottiformes	Cottidae	Enophrys bison	Buffalo Sculpin	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Cottidae	Hemilepidotus hemilepidotus	Red Irish Lord	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Cottidae	Hemilepidotus spinosus	Brown Irish Lord	X	X			X	X	#					X	2b
Cottiformes	Cottidae	Icelinus borealis	Northern Sculpin	X	X	X	X	X	X	X	X	X	X		X	1b
Cottiformes	Cottidae	Icelinus burchami	Dusky Sculpin				X		X		X					3a
Cottiformes	Cottidae	Icelinus filamentosus	Threadfin Sculpin		X	X	X		X	X	X		X		X	1b
Cottiformes	Cottidae	Icelinus fimbriatus	Fringed Sculpin								X					3b
Cottiformes	Cottidae	Icelinus tenuis	Spotfin Sculpin	X	X	X	X	#		X	X		X	X	X	1b
Cottiformes	Cottidae	Jordania zonope	Longfin Sculpin	X	X	#		X	X	X	X	X	X	X	X	1a
Cottiformes	Cottidae	Leptocottus armatus	Pacific Staghorn Sculpin	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Cottidae	Myoxocephalus polyacanthocephalus	Great Sculpin	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Cottidae	Oligocottus maculosus	Tidepool Sculpin	X	X	X	X	X	X	X	X	X	X	X	X	2c
Cottiformes	Cottidae	Oligocottus rimensis	Saddleback Sculpin		X				X		X				X	2c
Cottiformes	Cottidae	Oligocottus snyderi	Fluffy Sculpin						X	#						2c
Cottiformes	Cottidae	Paricelinus hopliticus	Thornback Sculpin							X	X					2b
Cottiformes	Cottidae	Radulinus asprellus	Slim Sculpin	X	X	X	X	X	X	X	X		X		X	2b
Cottiformes	Cottidae	Radulinus boleoides	Darter Sculpin		X				X				X			2b
Cottiformes	Cottidae	Ruscarius meanyi	Puget Sound Sculpin		X				X	X	X				X	2b
Cottiformes	Cottidae	Scorpaenichthys marmoratus	Cabezon	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Cottidae	Synchirus gilli	Manacled Sculpin	X	X		X	X	X	X	X	X	X		X	2b
Cottiformes	Cottidae	Triglops macellus	Roughspine Sculpin	X	X	X	X	X	X	X	X		X		X	1b
Cottiformes	Cottidae	Triglops pingelii	Ribbed Sculpin	X	X			X	X	X	X				X	1b
Cottiformes	Cryptacanthodidae	Cryptacanthodes aleutensis	Dwarf Wrymouth		X		X		X		X		X		X	3b
Cottiformes	Cryptacanthodidae	Cryptacanthodes giganteus	Giant Wrymouth		X				X		X				X	1a
Cottiformes	Cyclopteridae	Eumicrotremus orbis	Pacific Spiny Lumpsucker	X	X			X	X	X	X	X	X		X	1a
Cottiformes	Hemitripteridae	Blepsias cirrhosus	Silverspotted Sea Raven	X	X		X	X	X	X	X	X	X		X	1a
Cottiformes	Hemitripteridae	Nautichthys oculofasciatus	Sailfin Sea Raven	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Hexagrammidae	Hexagrammos decagrammus	Kelp Greenling	X	X	#		X	X	X	X	X	X	X	X	1a
Cottiformes	Hexagrammidae	Hexagrammos lagocephalus	Rock Greenling	X	X	#		X	X	X	X		X		X	2b
Cottiformes	Hexagrammidae	Hexagrammos stelleri	Whitespotted Greenling	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Hexagrammidae	Ophiodon elongatus	Lingcod	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Hexagrammidae	Oxylebius pictus	Painted Greenling	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Hexagrammidae	Zaniolepis latipinnis	Longspine Combfish	X	X	X	X		X	X	X	X	X	X	X	1a
Cottiformes	Liparidae	Careproctus melanurus	Blacktail Snailfish		X				X		X				X	3a
Cottiformes	Liparidae	Liparis callyodon	Spotted Snailfish	X	X			X	X		X				X	2c
Cottiformes	Liparidae	Liparis cyclopus	Ribbon Snailfish		X				X		X		X		X	2c
Cottiformes	Liparidae	Liparis dennyi	Marbled Snailfish	X	X			X	X		X		X	X	X	2c
Cottiformes	Liparidae	Liparis florae	Tidepool Snailfish	X	X			X	X		X				X	2c
Cottiformes	Liparidae	Liparis fucensis	Slipskin Snailfish	X	X				X		X		X		X	2c
Cottiformes	Liparidae	Liparis greeni	Lobefin Snailfish	#				X	X		X	#		#		2c
Cottiformes	Liparidae	Liparis mucosus	Slimy Snailfish						X							3a
Cottiformes	Liparidae	Liparis pulchellus	Showy Snailfish	X	X		X	X	X	X	X		X	X	X	1a
Cottiformes	Liparidae	Liparis rutteri	Ringtail Snailfish						X		X					3a
Cottiformes	Liparidae	Lipariscus nanus	Pygmy Snailfish								X					3a
Cottiformes	Liparidae	Nectoliparis pelagicus	Tadpole Snailfish		X		X				X		X		X	3a
Cottiformes	Liparidae	Paraliparis deani	Prickly Snailfish								X					3a
Cottiformes	Pholidae	Apodichthys fucorum	Rockweed Gunnel	X	X			X	X	X	X		X		X	2b
Cottiformes	Pholidae	Pholis clemensi	Longfin Gunnel	X	X	X	X	X	X	X	X	#		X	X	1a
Cottiformes	Pholidae	Pholis laeta	Crescent Gunnel	X	X	X	X	X	X	X	X	X	X	X	X	2c
Cottiformes	Pholidae	Pholis ornata	Saddleback Gunnel	X	X	X	X	X	X	X	X	X	X	X	X	2c
Cottiformes	Pholidae	Pholis schultzi	Red Gunnel	X	X			X	X			#			X	2b
Cottiformes	Psychrolutidae	Dasycottus setiger	Spiny Fathead	X	X		X	X	X	X	X		X	X	X	1a
Cottiformes	Psychrolutidae	Malacocottus kincaidi	Blackfin Fathead				X				X					3b
Cottiformes	Psychrolutidae	Malacocottus zonurus	Darkfin Fathead						X							3b
Cottiformes	Psychrolutidae	Psychrolutes paradoxus	Tadpole Fathead	X	X		X	X	X	X	X		X		X	1a
Cottiformes	Psychrolutidae	Psychrolutes sigalutes	Soft Fathead	X	X	X	X	X	X	X	X		X		X	2b
Cottiformes	Ptilichthyidae	Ptilichthys goodei	Quillfish	X	X	X	X		X	X	X				X	1a
Cottiformes	Rhamphocottidae	Rhamphocottus richardsonii	Grunt Sculpin	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Scytalinidae	Scytalina cerdale	Graveldiver						X							3a
Cottiformes	Stichaeidae	Anoplarchus insignis	Slender Cockscomb	X	X	#		X	X	X	X	X	X	X	X	2c
Cottiformes	Stichaeidae	Anoplarchus purpurescens	High Cockscomb	X	X	X	X	X	X	X	X	X	X	X	X	2c
Cottiformes	Stichaeidae	Chirolophis decoratus	Decorated Warbonnet	X	X	#		X	X	X	X	X	X	X	X	1a
Cottiformes	Stichaeidae	Chirolophis nugator	Mosshead Warbonnet	X	X	#		X	X	X	X	X	X	X	X	1a
Cottiformes	Stichaeidae	Leptoclinus maculatus	Daubed Shanny		X				X		X				X	1a
Cottiformes	Stichaeidae	Lumpenella longirostris	Longsnout Prickleback								X					2b
Cottiformes	Stichaeidae	Lumpenopsis hypochroma	Y-Prickleback								X					3a
Cottiformes	Stichaeidae	Lumpenus sagitta	Snake Prickleback	X	X	X	X	X	X	X	X	X	X	X	X	1a
Cottiformes	Stichaeidae	Phytichthys chirus	Ribbon Prickleback		X				X	X	X		X	X	X	2c
Cottiformes	Stichaeidae	Plectobranchus evides	Bluebarred Prickleback		X	X	X				X		X		X	1a
Cottiformes	Stichaeidae	Poroclinus rothrocki	Whitebarred Prickleback		X		X		X		X		X		X	2b
Cottiformes	Stichaeidae	Xiphister atropurpureus	Black Prickleback		X			X	X		X		X		X	2c
Cottiformes	Stichaeidae	Xiphister mucosus	Rock Prickleback	X	X			X	X	X	X				X	2c
Cottiformes	Zaproridae	Zaprora silenus	Prowfish		X				X		X		X			2a
Cottiformes	Zoarcidae	Lycodapus mandibularis	Pallid Eelpout		X		X				X		X		X	3a
Cottiformes	Zoarcidae	Lycodapus parviceps	Smallhead Eelpout						X		X					3a
Cottiformes	Zoarcidae	Lycodes beringi	Bering Eelpout		X		X		X		X				X	3b
Cottiformes	Zoarcidae	Lycodes brevipes	Shortfin Eelpout		X				X		X		X		X	2b
Cottiformes	Zoarcidae	Lycodes cortezianus	Bigfin Eelpout		X				X						X	3b
Cottiformes	Zoarcidae	Lycodes pacificus	Blackbelly Eelpout	X	X	X	X	X	X	X	X	X	X	X	X	2c
Cottiformes	Zoarcidae	Lycodes palearis	Wattled Eelpout		X		X		X		X				X	2c
Cypriniformes	Cyprinidae	Cyprinus carpio	Common Carp								X					2a
Cyprinodontiformes	Cyprinodontidae	Cyprinodon variegatus	Sheepshead Minnow						X							2a
Gadiformes	Gadidae	Gadus macrocephalus	Pacific Cod	X	X	X	X	X	X	X	X		X	X	X	1b
Gadiformes	Gadidae	Microgadus proximus	Pacific Tomcod	X	X	X	X	X	X	X	X	X	X	X	X	1b
Gadiformes	Gadidae	Theragra chalcogramma	Walleye Pollock	X	X	X	X	X	X	X	X	X	X	X	X	1b
Gadiformes	Merlucciidae	Merluccius productus	Pacific Hake		X	X	X		X		X		X		X	1a
Gasterosteiformes	Aulorhynchidae	Aulorhynchus flavidus	Tubesnout	X	X	X	X	X	X	X	X	X	X	X	X	1a
Gasterosteiformes	Gasterosteidae	Gasterosteus aculeatus	Threespine Stickleback	X	X	X	X	X	X	X	X		X	X	X	1a
Gasterosteiformes	Syngnathidae	Syngnathus leptorhynchus	Bay Pipefish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Gobiesociformes	Gobiesocidae	Gobiesox maeandricus	Northern Clingfish	X	X	#		X	X	X	X	#			X	1a
Hexanchiformes	Hexanchidae	Hexanchus griseus	Bluntnose Sixgill Shark	X	X	X	X	X	X	X	X	X	X	X	X	1a
Hexanchiformes	Hexanchidae	Notorynchus cepedianus	Broadnose Sevengill Shark		X						X		X			2a
Lamniformes	Alopiidae	Alopias vulpinus	Common Thresher Shark						X							1a
Lamniformes	Cetorhinidae	Cetorhinus maximus	Basking Shark		X				X		X		X		X	1a
Lamniformes	Lamnidae	Lamna ditropis	Salmon Shark		X				X		X				X	1a
Lampriformes	Lampridae	Lampris guttatus	Opah		X				X						X	2a
Lampriformes	Trachipteridae	Trachipterus altivelis	King-of-the-Salmon		X		X		X		X		X			2a
Myctophiformes	Myctophidae	Diaphus theta	California Headlightfish		X		X		X		X		X		X	3a
Myctophiformes	Myctophidae	Nannobrachium regale	Pinpoint Lampfish								X					3a
Myctophiformes	Myctophidae	Protomyctophum crockeri	California Flashlightfish								X					3a
Myctophiformes	Myctophidae	Protomyctophum thompsoni	Northern Flashlightfish						X							3a
Myctophiformes	Myctophidae	Stenobrachius leucopsarus	Northern Lampfish		X				X				X		X	3a
Myctophiformes	Myctophidae	Tarletonbeania crenularis	Blue Lanternfish						X							3a
Myxiniformes	Myxinidae	Eptatretus stoutii	Pacific Hagfish		X				X						X	2a
Ophidiiformes	Bythitidae	Brosmophycis marginata	Red Brotula	X	X	X	X	X	X	X	X		X	X	X	1a
Ophidiiformes	Ophidiidea	Chilara taylori	Spotted Cusk-eel								X					1a
Osmeriformes	Osmeridae	Allosmerus elongatus	Whitebait Smelt						X							3a
Osmeriformes	Osmeridae	Hypomesus pretiosus	Surf Smelt	X	X	X	X	X	X	X	X		X		X	2b
Osmeriformes	Osmeridae	Mallotus villosus	Pacific Capelin						X							2b
Osmeriformes	Osmeridae	Spirinchus starksi	Night Smelt						X							3a
Osmeriformes	Osmeridae	Spirinchus thaleichthys	Longfin Smelt		X		X		X		X		X		X	2b
Osmeriformes	Osmeridae	Thaleichthys pacificus	Eulachon		X				X		X		X		X	2b
Perciformes	Ammodytidae	Ammodytes personatus	Pacific Sand Lance	X	X	X	X	X	X	X	X	X	X	X	X	1a
Perciformes	Bramidae	Brama japonica	Pacific Pomfret		X										X	2a
Perciformes	Carangidae	Trachurus symmetricus	Jack Mackerel		X								X			2a
Perciformes	Centrolophidae	Icichthys lockingtoni	Medusafish						X				X			2a
Perciformes	Clinidae	Gibbonsia metzi	Striped Kelpfish					#								1a
Perciformes	Embiotocidae	Amphistichus rhodoterus	Redtail Surfperch						X							3b
Perciformes	Embiotocidae	Brachyistius frenatus	Kelp Perch	X	X	X	X	X	X	X	X	X	X	X	X	1a
Perciformes	Embiotocidae	Cymatogaster aggregata	Shiner Perch	X	X	X	X	X	X	X	X	X	X	X	X	1a
Perciformes	Embiotocidae	Embiotoca lateralis	Striped Seaperch	X	X	X	X	X	X	X	X	X	X	X	X	1a
Perciformes	Embiotocidae	Hyperprosopon ellipticum	Silver Surfperch		X				X						X	2b
Perciformes	Embiotocidae	Phanerodon furcatus	White Seaperch		X		X		X		X				X	2b
Perciformes	Embiotocidae	Rhacochilus vacca	Pile Perch	X	X	X	X	X	X	X	X	X	X	X	X	1a
Perciformes	Gobiidae	Clevelandia ios	Arrow Goby		X		X		X		X		X		X	2b
Perciformes	Gobiidae	Lepidogobius lepidus	Bay Goby	X	X	X	X	X	X	X	X		X	X	X	2c
Perciformes	Gobiidae	Rhinogobiops nicholsii	Blackeye Goby	X	X	X	X	X	X	X	X	X	X	X	X	1a
Perciformes	Icosteidae	Icosteus aenigmaticus	Ragfish		X				X				X		X	2a
Perciformes	Moronidae	Morone saxatilis	Striped Bass		X				X				X		X	2a
Perciformes	Sciaenidae	Atractoscion nobilis	White Seabass		X				X		X				X	2b
Perciformes	Sciaenidae	Genyonemus lineatus	White Croaker		X						X		X		X	2b
Perciformes	Sciaenidae	Seriphus politus	Queenfish		X				X		X				X	2b
Perciformes	Scombridae	Sarda chiliensis	Pacific Bonito		X		X		X		X		X		X	3b
Perciformes	Scombridae	Scomber japonicus	Pacific Chub Mackerel		X				X		X		X		X	3b
Perciformes	Sphyraenidae	Sphyraena argentea	Pacific Barracuda		X				X				X		X	2a
Perciformes	Stromateidae	Peprilus simillimus	Pacific Pompano		X		X		X		X		X		X	1a
Perciformes	Trichiuridae	Benthodesmus pacificus	North Pacific Frostfish						X							3a
Perciformes	Trichiuridae	Benthodesmus tenuis	Slender Frostfish		X				X						X	3a
Perciformes	Trichodontidae	Trichodon trichodon	Pacific Sandfish		X				X		X				X	1a
Petromyzontiformes	Petromyzontidae	Entosphenus tridentatus	Pacific Lamprey		X		X		X		X		X		X	2b
Petromyzontiformes	Petromyzontidae	Lampetra ayresii	Western River Lamprey		X				X		X		X		X	2b
Pleuronectiformes	Cynoglossidae	Symphurus atricaudus	California Tonguefish						X							2b
Pleuronectiformes	Paralichthyidae	Citharichthys sordidus	Pacific Sanddab	X	X	X	X	X	X	X	X	X	X	X	X	1b
Pleuronectiformes	Paralichthyidae	Citharichthys stigmaeus	Speckled Sanddab	X	X	X	X	X	X	X	X	X	X	X	X	1b
Pleuronectiformes	Pleuronectidae	Atheresthes stomias	Arrowtooth Flounder		X		X		X		X		X		X	2b
Pleuronectiformes	Pleuronectidae	Eopsetta jordani	Petrale Sole		X		X		X		X		X		X	2b
Pleuronectiformes	Pleuronectidae	Glyptocephalus zachirus	Rex Sole	X	X	X	X		X		X		X		X	1b
Pleuronectiformes	Pleuronectidae	Hippoglossoides elassodon	Flathead Sole		X		X		X	X	X		X		X	1b
Pleuronectiformes	Pleuronectidae	Hippoglossus stenolepis	Pacific Halibut		X		X	X	X		X		X		X	1a
Pleuronectiformes	Pleuronectidae	Isopsetta isolepis	Butter Sole		X		X	X	X		X	X	X		X	2c
Pleuronectiformes	Pleuronectidae	Lepidopsetta bilineata	Southern Rock Sole	X	X	X	X	X	X	X	X	X	X	X	X	2c
Pleuronectiformes	Pleuronectidae	Lepidopsetta polyxystra	Northern Rock Sole		X		X		X		X		X		X	2c
Pleuronectiformes	Pleuronectidae	Limanda aspera	Yellowfin Sole						X							2c
Pleuronectiformes	Pleuronectidae	Lyopsetta exilis	Slender Sole	X	X	X	X	X	X	X	X	X	X	X	X	1b
Pleuronectiformes	Pleuronectidae	Microstomus pacificus	Dover Sole	X	X		X	X	X	X	X		X		X	1b
Pleuronectiformes	Pleuronectidae	Parophrys vetulus	English Sole	X	X	X	X	X	X	X	X	X	X	X	X	1b
Pleuronectiformes	Pleuronectidae	Platichthys stellatus	Starry Flounder	X	X	X	X	X	X	X	X	X	X	X	X	1b
Pleuronectiformes	Pleuronectidae	Pleuronichthys coenosus	C-O Sole	X	X	X	X	X	X	X	X	X	X	X	X	1a
Pleuronectiformes	Pleuronectidae	Pleuronichthys decurrens	Curlfin Sole		X				X				X		X	2b
Pleuronectiformes	Pleuronectidae	Psettichthys melanostictus	Sand Sole	X	X	X	X	X	X		X		X		X	1b
Rajiformes	Rajiformes	Bathyraja interrupta	Bering Skate								X					3a
Rajiformes	Rajiformes	Bathyraja kincaidii	Sandpaper Skate						X		X					3a
Rajiformes	Rajiformes	Beringraja binoculata	Big Skate	X	X	X	X	X	X	X	X	X	X	X	X	1a
Rajiformes	Rajiformes	Raja inornata	California Skate						X							1a
Rajiformes	Rajiformes	Raja rhina	Longnose Skate	X	X	X	X		X		X		X	X	X	1a
Salmoniformes	Salmonidae	Oncorhynchus clarkii	Cutthroat Trout	X	X		X		X		X		X		X	1a
Salmoniformes	Salmonidae	Oncorhynchus gorbuscha	Pink Salmon		X		X		X		X		X	X	X	1a
Salmoniformes	Salmonidae	Oncorhynchus keta	Chum Salmon		X		X		X	X	X		X		X	1a
Salmoniformes	Salmonidae	Oncorhynchus kisutch	Coho Salmon	X	X		X		X	X	X		X		X	1a
Salmoniformes	Salmonidae	Oncorhynchus mykiss	Steelhead (Rainbow Trout)		X		X		X		X		X	X	X	1a
Salmoniformes	Salmonidae	Oncorhynchus nerka	Sockeye Salmon		X		X		X		X		X		X	1a
Salmoniformes	Salmonidae	Oncorhynchus tshawytscha	Chinook Salmon	X	X		X		X		X		X	X	X	1a
Salmoniformes	Salmonidae	Salmo salar	Atlantic Salmon		X		X		X		X		X		X	1a
Salmoniformes	Salmonidae	Salvelinus confluentus	Bull Trout		X		X		X		X		X		X	2b
Salmoniformes	Salmonidae	Salvelinus malma	Dolly Varden		X		X		X		X		X		X	2b
Scorpaeniformes	Scorpaenidae	Sebastes aleutianus	Rougheye Rockfish		X				X						X	2a
Scorpaeniformes	Scorpaenidae	Sebastes alutus	Pacific Ocean Perch						X		X				X	2b
Scorpaeniformes	Scorpaenidae	Sebastes auriculatus	Brown Rockfish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Scorpaeniformes	Scorpaenidae	Sebastes babcocki	Redbanded Rockfish				X		X							2a
Scorpaeniformes	Scorpaenidae	Sebastes brevispinis	Silvergray Rockfish	X	X	#		X	X				X			1a
Scorpaeniformes	Scorpaenidae	Sebastes caurinus	Copper Rockfish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Scorpaeniformes	Scorpaenidae	Sebastes crameri	Darkblotched Rockfish		X				X		X				X	2a
Scorpaeniformes	Scorpaenidae	Sebastes diaconus	Deacon Rockfish			#		X	X	X	X					2c
Scorpaeniformes	Scorpaenidae	Sebastes diploproa	Splitnose Rockfish		X		X		X		X				X	2b
Scorpaeniformes	Scorpaenidae	Sebastes elongatus	Greenstriped Rockfish		X		X		X	X	X		X		X	1a
Scorpaeniformes	Scorpaenidae	Sebastes emphaeus	Puget Sound Rockfish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Scorpaeniformes	Scorpaenidae	Sebastes entomelas	Widow Rockfish		X			X	X	#					X	1a
Scorpaeniformes	Scorpaenidae	Sebastes flavidus	Yellowtail Rockfish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Scorpaeniformes	Scorpaenidae	Sebastes helvomaculatus	Rosethorn Rockfish		X				X						X	3b
Scorpaeniformes	Scorpaenidae	Sebastes maliger	Quillback Rockfish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Scorpaeniformes	Scorpaenidae	Sebastes melanops	Black Rockfish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Scorpaeniformes	Scorpaenidae	Sebastes miniatus	Vermilion Rockfish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Scorpaeniformes	Scorpaenidae	Sebastes nebulosus	China Rockfish	X	X	#		X	X	X	X				X	1a
Scorpaeniformes	Scorpaenidae	Sebastes nigrocinctus	Tiger Rockfish	X	X			X	X	X	X				X	1a
Scorpaeniformes	Scorpaenidae	Sebastes paucispinis	Bocaccio	X	X	X	X	X	X	X	X		X		X	1a
Scorpaeniformes	Scorpaenidae	Sebastes pinniger	Canary Rockfish	X	X	X	X	X	X	X	X		X		X	1a
Scorpaeniformes	Scorpaenidae	Sebastes proriger	Redstripe Rockfish	X	X	X	X		X		X		X	X	X	1a
Scorpaeniformes	Scorpaenidae	Sebastes rosaceus	Rosy Rockfish		X				X						X	2b
Scorpaeniformes	Scorpaenidae	Sebastes ruberrimus	Yelloweye Rockfish	X	X	X	X	X	X	X	X		X	X	X	1a
Scorpaeniformes	Scorpaenidae	Sebastes saxicola	Stripetail Rockfish		X		X		X		X		X		X	3b
Scorpaeniformes	Scorpaenidae	Sebastes semicinctus	Halfbanded Rockfish						X							2a
Scorpaeniformes	Scorpaenidae	Sebastes zacentrus	Sharpchin Rockfish		X	X		X	X		X		X		X	2b
Scorpaeniformes	Scorpaenidae	Sebastolobus alascanus	Shortspine Thornyhead		X		X		X		X		X		X	2b
Squaliformes	Somniosidae	Somniosus pacificus	Pacific Sleeper Shark		X				X		X				X	2a
Squaliformes	Squalidae	Squalus suckleyi	Spotted Spiny Dogfish	X	X	X	X	X	X	X	X	X	X	X	X	1a
Squatiniformes	Squatinidae	Squatina californica	Pacific Angel Shark		X										X	1a
Stomiiformes	Sternoptychidae	Argyropelecus sladeni	Lowcrest Hatchetfish								X					3a
Stomiiformes	Stomiidae	Chauliodus macouni	Pacific Viperfish						X		X					2a
Tetraodontiformes	Molidae	Mola mola	Ocean Sunfish		X			X	X		X		X		X	1a
Torpediniformes	Torpedinidae	Torpedo californica	Pacific Electric Ray	X	X		X		X		X	X	X		X	1a

Originally as Pallasina barbata, see Stevenson et al. (2021)

Identification confidence categories

We created an identification key to separate fishes known to inhabit the Salish Sea (Pietsch & Orr, 2019) into ranked categories indicating their suitability for visual census (Fig. 1) based on ease of visual identification and the potential for encounter on dives. For each species, we determined if a fish could be visually identified, and if so, whether the validity of a sighting benefits from a verifying photograph or if identification requires a specimen in hand. Species requiring a photograph included those that were rare or beyond diving range (not both), very similar in appearance to a sympatric species (e.g., Icelinus borealis — Northern Sculpin vs. Icelinus fimbriatus — Fringed Sculpin), or easily misidentified (Liparis spp. — Snailfishes). Fishes that required a specimen in hand for identification were those for which identification requires scale or spine counts or other measurements not possible from photographs (e.g., Bathyagonus spp. — Starsnouts).

Fig. 1

Identification key used to independently assign each Salish Sea fish species a detectability category for visual surveys. A given fish species can belong to one of three categories: category 1 — conspicuous and distinctive, with no photograph or specimen necessary for verification; category 2 — requires photographic evidence to be confidently reported on a visual survey; category 3 — has physical or life history characteristics that require a specimen in hand for identification to species. Sub-categories a, b, and c provide the rationale for assignment of a species to category 1, 2, or 3

As per the identification key (Fig. 1), category 1 fishes are unmistakable (category 1a) or are visually identifiable, occur at diving depths, and are not rare in the Salish Sea (category 1b). Category 2 fishes (a) are unmistakable but not typically found at diving depths; (b) are rare in the Salish Sea but live within diving depths (e.g., Lumpenopsis hypochroma — Y-Prickleback), or are not rare but exceed diving depths (e.g., Lycodes palearis — Wattled Eelpout); or (c) look very similar to other species (e.g., Sarda chiliensis — Pacific Bonito and Scomber japonicus — Pacific Chub Mackerel). These species would benefit from photographic evidence for confident reporting on a visual survey. Category 3 fish species have physical characteristics discernable only with a specimen in hand (category 3a) or are both rare in the Salish Sea and beyond diving depths (category 3b).

Results

From 1998 to 2019, expert REEF divers conducted 13,274 Volunteer Fish Survey Project surveys in the Salish Sea (REEF, 2020). Most of these surveys were conducted in rocky habitats (52%), including rock or shale reefs and boulder fields, or on artificial reefs (35%), such as shipwrecks and other man-made structures. The remaining were performed over other habitat types including mud/silt, surfgrass and eelgrass, or open ocean. The largest percentage of surveys were recorded in Central Basin (39%), followed by Northern Straits (27%), the Strait of Georgia (15%), and Hood Canal (13%). South Puget Sound and Whidbey Basin comprised the smallest percentage of surveys (4% and 2%, respectively) (Supplemental Map).

Based on all REEF expert surveys conducted during the study period, REEF volunteers reported 137 of the 260 species listed in Pietsch and Orr (2019), as well as one additional species not included in the original species inventory. This brings the total number of fish species known to occur in the Salish Sea to 261. Table 1 lists the category and sub-category (e.g., 1a) of each species in accordance with the identification key (Fig. 1). We determined that 85% (n = 223) of the 261 species (Table 1) are visually identifiable (categories 1 and 2). Of the 223 species for which visual observation and subsequent positive identification is possible, 120 species are considered conspicuous and distinctive, not rare in the Salish Sea, and present in habitats likely to be visually surveyed by divers (category 1). These category 1 fishes can be reported with high confidence without a photograph and have the highest potential for documentation by REEF surveyors. The other 103 visually identifiable species were less likely to be documented on REEF surveys because they (1) are typically oceanic or found outside diving depths, (2) are considered vagrants or rare, (3) behave in a manner that evades visual detection by divers (e.g., cryptic, nocturnal), or (4) are difficult, but not impossible, to distinguish from sympatric species (category 2). In these cases, photographic evidence may be necessary to aid or confirm positive identification. The remaining 38 species known to occur in the Salish Sea (Pietsch & Orr, 2019) are assumed to require a specimen in hand for definitive identification or are extremely unlikely to be sighted due to rarity and bathypelagic or bathydemersal habitat preferences (category 3). From 1998 to 2019, REEF divers sighted 85% (102 of 120) of category 1 species, and 35% (36 of 103) of category 2 species.

We identified one novel species, Gibbonsia metzi — Striped Kelpfish, that had valid REEF sightings in the Salish Sea but was not included in Pietsch and Orr (2019). REEF divers documented this species near Cape Flattery, Washington, once in 2006 and again in 2007. This species is easily recognizable (category 1) and commonly sighted on the outer coasts of Vancouver Island and Washington, just beyond the Salish Sea’s westernmost border.

Consistent with our hypothesis, RDT surveys helped to fill knowledge gaps in the spatial distributions of species inhabiting rocky reef or kelp habitats at diving depths. REEF divers recorded the novel presence of ten category 1 species in one or more basins previously not documented by Pietsch and Orr (2019): Sebastes brevispinis — Silvergray Rockfish, S. emphaeus — Widow Rockfish, S. flavidus — China Rockfish; Hexagrammos decagrammus — Kelp Greenling, Chirolophis decoratus — Decorated Warbonnet, C. nugator — Mosshead Warbonnet, Pholis clemensi — Longfin Gunnel, Gobiesox maeandricus — Northern Clingfish, Icelinus tenuis — Spotfin Sculpin, and Jordania zonope — Longfin Sculpin. Similarly, REEF survey data showed that eight category 2 species were found to have a wider range within the Salish Sea: Asemichthys taylori — Spinynose Sculpin, Hemilepidotus spinosus — Brown Irish Lord, Oligocottus snyderi — Fluffy Sculpin, Hexagrammos lagocephalus — Rock Greenling, Liparis greeni — Lobefin Snailfish, Sebastes diaconus — Deacon Rockfish, Anoplarchus insignis — Slender Cockscomb, and Pholis schultzi — Red Gunnel. These 18 species are denoted with a “#” in Table 1.

Discussion

In an era in which marine ecosystems are at risk from a suite of anthropogenic stressors, it is critical to strengthen biodiversity monitoring efforts that can inform policy and management (Friedman et al., 2020). Using robust citizen science to document species distributions can permit more comprehensive tracking of temporal and spatial population changes, provided managers understand the value and limitations of the data (Burgess et al., 2016). Trained, expert-level participants in REEF’s Volunteer Fish Survey Project were able to expand the known range of 18 fish species and add Gibbonsia metzi to a previously established list of 260 fish species known to occur in the Salish Sea. Additionally, in the face of nearshore habitat loss, ocean acidification, warming ocean temperatures, shifting prey bases, and other threats to marine fishes, volunteer divers play an important role in helping state and federal agencies monitor species of concern, such as rockfishes (Sebastes spp.; Tolimieri et al., 2017). For example, two rockfishes documented on REEF surveys, S. entomelas — Widow Rockfish, and S. nebulosus — China Rockfish, are candidates for listing as species of special concern in Washington, and existing reports of S. entomelas within the Salish Sea are rare (Pietsch & Orr, 2019).

Based on our categorization system, 223 of 261 species known to occur in the Salish Sea are visually distinguishable, without the need for a specimen in hand. A large majority (102 of 120, or 85%) of the species most likely to be encountered and identified on a dive (category 1) were documented on REEF RDT surveys. An additional 36 species considered rare, uncommon in dive habitats, or visually similar to other species (category 2) were documented on RDT surveys. These records benefit from photographic evidence for verification, which is often provided to REEF during their quality assurance and control process. Many of the 81 undetected category 1 and category 2 fishes, while visually identifiable if encountered, were likely not documented by REEF volunteers because of the rarity of the species in the Salish Sea or because of a preferred habitat, depth range, behavior, or crypticity not well-suited for RDT. For example, the Pacific Viperfish (Chauliodus macouni), a category 2 species, is unmistakable, but it will likely never be seen by a REEF diver because it typically lives in thousands of meters of water. The common thresher shark (Alopias vlupinus) is a universally recognizable fish (category 1) that has been documented in the Salish Sea. The life history of this shark, however, would typically preclude it from the most common dive habitats. Similarly, category 2 flatfishes like the Petrale Sole (Eopsetta jordani) and Arrowtooth Flounder (Atheresthes stomias) are identifiable but are likely underrepresented in REEF data because only a small percentage of RDT surveys (7%) are conducted in soft-bottom habitats.

The categorization system described here relies on having an expert (such as a taxonomist) familiar enough with local fishes to determine if a species could be identified visually by trained individuals or must be identified in-hand. Categories can be used for quality control and assurance by identifying potentially erroneous sightings or to verify sightings prior to their entry into databases, as well as to gauge the detection likelihood of any given species on a visual survey. A similar scoring system might be useful in other ecosystems monitored by trained volunteers to improve data collection rigor or inform diver education.

REEF divers sighted 62% (138 of 223) of the visually detectable species occurring in the Salish Sea, suggesting that citizen science data collection is a highly valuable monitoring tool for the majority of species in the region. Furthermore, REEF data are provided continuously at no cost to the government agencies entrusted to manage this marine ecosystem. While we did not explore temporal trends in this study, REEF surveys are conducted year-round and consistently year after year, and data are publicly accessible soon after surveys are conducted. This makes citizen science an appropriate tool for tracking fish species diversity and distribution over time.

Conclusions

Trained recreational divers provide an important data stream for documenting fish species occupancy, abundance, and distribution in the Salish Sea. In just over 20 years, expert-level REEF citizen scientists spent 11,918 h underwater conducting 13,274 surveys, generating data that expanded the known distribution of 18 species and identified a species not previously included in the list of recognized fishes for the ecosystem. Furthermore, by assigning detectability scores to RDT survey data, we show that expert surveyors collected reliable data on 53% of the ecosystem’s total known fish species. While the degree to which visual survey methods are useful for biodiversity monitoring varies by ecosystem, monitoring data gathered by citizen scientists can be a highly beneficial resource for management agencies to supplement fisheries-dependent and agency-sponsored, fisheries-independent monitoring.

Below is the link to the electronic supplementary material.

Supplementary file1 (PNG 2235 KB)