Barred Sand Bass Spawning Movements and Habitat Characterization

Background

Barred sand bass, Paralabrax nebulifer, continues to be one of the most sought-after sport fish in southern California. Since the 1960s, this species has ranked among the top ten sport fish caught by commercial passenger fishing vessels (CPFVs), or "party boats," in southern California, with annual catches averaging nearly one million fish over the last 20 years. For decades, CPFVs and private recreational boaters have targeted well-known spawning aggregation sites throughout southern California, including the Ventura Flats, Santa Monica Bay, Huntington Beach Flats, San Onofre, and San Diego. Approximately 71 percent of the annual barred sand bass catch is harvested by the CPFV fleet from June through August, during peak spawning season.

From 1961 to 2008, barred sand bass catches increased to a high in 2000 and have dramatically declined since. These dramatic catch declines in recent years have caused concern among fisheries biologists and fishermen alike. Answering questions regarding barred sand bass spawning movements and spawning habitat requirements will be important for the management of this resource.

"Hotspot" Analysis

Barred sand bass catch location data was compiled by California Recreational Fisheries Survey (CRFS) samplers for private/rental boats from 2004-2008 in the southern California region. CRFS samplers interview anglers at public launch facilities, asking questions about their fishing activities, examining their catch to determine the number and species of fish kept or discarded, weighing and measuring the catch, and collecting fishing location and depth information. The catch location data were mapped and analyzed using a Geographic Information System (GIS) and major "hotspot" catch locations (potential spawning grounds) were identified. This analysis provides valuable information about where and when barred sand bass spawning aggregations may occur in southern California. In addition, areas fished around Huntington Beach were examined on a finer scale to examine any seasonal patterns of catch.

Spawning Movements

In the 1960s and 1990s, biologists with the DFG tagged a total of 9,000 barred sand bass in southern California. The recapture information from these two time periods enabled us to document large-scale spawning-related movements of barred sand bass for the first time. Using this dataset we have attempted to discover 1) how long individual barred sand bass remain at spawning grounds during spawning season, 2) how far fish migrate to spawn, and 3) whether fish show fidelity to certain spawning locations.

In addition to large-scale spawning movements, we are also interested in the short-term, fine-scale spawning movements of barred sand bass. To address this, project staff work with Dr. Chris Lowe at California State University, Long Beach. Project staff assist with field research that uses state-of-the-art technology to actively track adult barred sand bass at Huntington Flats during the spawning season. Fish are surgically fitted with acoustic transmitters and then followed by boat using an underwater hydrophone. Each transmitter contains a depth sensor which emits a signal that allows the researcher to determine both the horizontal and vertical movements of the fish every two seconds. Results from these data will enable us to determine 1) the size of area used daily by individuals during peak spawning season, 2) what time of day they spawn based on their vertical movements in the water column, and 3) how frequently they spawn.

(1) With the fish immersed in a saltwater anesthetic bath, the transmitter is inserted through a small incision in the lower abdominal cavity.
(2) Two to three sutures are used to close the incision.
(3) Prior to release, the fish is measured and fitted with an external dart tag for easy identification upon recapture.
DFG photos by E. Jarvis

Spawning Habitat

For other aggregate spawners, the timing and location of spawning aggregations are related to water temperature, lunar activity, and currents. However, depth and bottom habitat type are the only characteristics documented in historical descriptions of barred sand bass spawning aggregation sites. To understand whether barred sand bass spawning aggregation sites are unique, Scuba Assessment Project staff conducted field surveys to describe the typical oceanographic (e.g., water temperature), habitat (e.g., type of substrate), and biological features (e.g., invertebrates living on and in the substrate) of areas where spawning aggregations occur and areas where spawning aggregations are absent.

Findings to Date

"Hotspot" Analysis

Five "hotspots" for barred sand bass catch were identified during the summer months, which are likely major spawning grounds for this species. The proportion of catch varied among these "hotspots" from 2004 to 2008 with Huntington Flats off Orange County and Imperial Beach ("I.B." Flats) on the U.S./Mexico border in San Diego County being the top catch locations. On a finer scale, natural reefs (Horseshoe Kelp and Palos Verdes Peninsula) and artificial structures (reefs, oil rigs, and breakwaters) were more important catch locations in the Huntington Beach Flats area outside of peak spawning season. This suggests that areas with higher relief or structure may serve as important habitat for barred sand bass before and after spawning activities.

Map of the Southern California Bight showing the number of barred sand bass kept and released by private/rental boats from 2004-2008 by 1x1 mile fishing block from June - August. The percentages represent the proportion of barred sand bass caught by county and standardized by area (1x1 mile fishing block).

Spawning movements

Tag and recapture data

Overall, the DFG received 972 barred sand bass tag returns from tagging efforts conducted in the 1960s and 1990s (an 11 percent recapture rate). Based on recapture frequencies, it appears that barred sand bass individuals remain on spawning grounds (e.g., Huntington Beach Flats) for at least one month during peak spawning season. Following spawning season, some fish remain, while others move away. The average migration distance from spawning locations was about 15 miles, although it appears that not all individuals at spawning grounds migrate to the same locations after spawning season. Overall, the farthest recapture distance was approximately 57 miles. Annual patterns in the timing and occurrence of recaptures strongly suggest barred sand bass visit the same spawning grounds year after year.

Acoustic telemetry data

Data collection is currently underway. Stay tuned!

Spawning habitat

Data analysis is currently underway. Stay tuned!