Abundance of Rocky Reef Fishes, Invertebrates and Algae, Reef Check California (RCCA), 2006 - 2017

Study Extent

Sites are selected by Reef Check California (RCCA) dive teams using RCCA protocol. A site is defined as a location containing shallow rocky reef/kelp forest habitat that is 250 linear meters of coastline in size unless otherwise distinguished by distinct geological features (e.g., a bay). Priority is given to sites that are inside or near existing or planned Marine Protected Areas, so that trends can be compared between protected areas and areas open to fishing.

Sampling

A survey, at minimum, consists of 18 band transects: 6 core transects and 12 fish-only transects. During each transect, an area of 30 m x 2 m is surveyed (60 m2) in approximately 10-15 minutes. Half of the transects (3 core and 6 fish-only) are conducted inshore in shallower waters, while the other half are conducted offshore in deeper waters. Transects must be haphazardly placed in rocky reef habitat, spaced at least 5 m apart, and follow a depth contour as much as possible. No transects are conducted at depths greater than 18 m. During each core transect, divers search for invertebrates, kelp, and fish. They also perform a Uniform Point Contact (UPC) survey to characterize the substrate, its topography, and any organisms directly covering it. Divers are required to use a flashlight, and are instructed to search the transect area as thoroughly as possible while remaining approximately within the 10-15 minute survey interval. Fish are surveyed first, while laying the transect tape, so that their behavior is minimally affected by the divers' presence. Before beginning, divers assess visibility: One diver holds up a hand, and the other diver swims away until they can no longer distinguish the fingers. This distance defines the visibility measurement; a visibility of at least 3 m is required to perform fish surveys. If the visibility is sufficient, divers search for fish within the 30 m x 2 m transect area, up to a height of 2 m off the bottom, for a total survey volume of 120 m3. They identify and size all fish observed that are part of the RCCA's list of 35 key fish taxa. Size is estimated by eye to the nearest centimeter. If a large number of fish of the same species is observed, divers may estimate the minimum and maximum size of the group. Young of the year rockfish (Genus Sebastes) are always given a minimum size of 1 cm and a maximum size of 10 cm. Divers also record the presence or absence of all invertebrates and algae from the RCCA's list of key taxa during core transects. Invertebrates must be at least 2.5 cm in size to be recorded, except for anemones (Order Actinaria) and gorgonians (Genuses Muricea and Leptogorgia). Anemones must be at least 10 cm tall or wide while gorgonians must be at least 10 cm tall. If divers encounter a large density of a particular invertebrate taxa, that taxa may be subsampled. To subsample, divers count 50 individuals, and then note where they are along the transect line (e.g., 50 urchins were observed in 17 m). Red abalone (Haliotis rufescens) are not subsampled. Densities for subsampled taxa have already been adjusted to have units of number of individuals per 60 m2 in this data submission. When giant kelp (Macrocystis pyrifera) are observed, the number of stipes for each individual is recorded. Finally, as part of the UPC survey, divers examine the substrate at each of 30 points at 1 m intervals along the transect tape and characterize it as one of 5 categories: sand, cobble, boulder, bedrock and other. At each point, the topography, or relief, of the substrate is also characterized as one of 4 categories: 0-10 cm, 10 cm - 1 m, > 1 m - 2 m, and > 2 m. Finally, divers record which organisms (if any) are covering the substrate at each point. In addition to the 6 core transects, divers also perform 12 fish-only transects (6 inshore and 6 offshore). Occasionally, more than 12 fish-only transects are performed. All fish-only transects use the same protocols for fish surveys described above. For additional details on survey methods, see the RCCA monitoring protocol, available here: https://opc.dataone.org/view/doi%3A10.25494%2FP69885

Quality Control

For all survey types, divers record data on a slate while underwater. At the end of each dive, divers tally up the total numbers of individuals of each species observed. They ensure that all data are complete and totaled correctly and that all writing is legible. For fish transects, another diver reviews the data sheet as an additional quality assurance step. After a survey is complete, the data are entered into an online database and the original data sheets are sent to RCCA.

Method steps

1. Data were retrieved from where they are archived on the Ocean Protection Council's DataONE node and saved in Comma Separated Values (.csv) files.
2. Data were transformed from the native format output into a table structure using Darwin Core Archive (DwC-A, occurrence core, measurement or fact extension) term names as column names. Python 3 processing scripts were used to run the data format conversion.

The coast of southern Oregon and California.