COS 82-4
Spatial and temporal size segregation in southern California yellowtail (Seriola lalandi): Results from recreational fishery data and conventional tagging
California has begun an ambitious program of marine spatial management. The design of coherent management, however, depends upon understanding spatial and temporal patterns of targeted species as well as how their behavior and habitat usage (spawning, feeding, etc.) changes ontogenetically. While spatial data are available for some exploited fish species within the Southern California Bight (SCB), yellowtail (Seriola lalandi) are not one. This is because although highly sought-after, they do not fit within existing federal or state management strategies, thus their larger ecological role within the marine community remains vague.
Yellowtail are highly mobile, predatory jacks found along the Pacific coast of southern California and Baja California, Mexico and are intensely targeted in both Mexican and United States’ waters. The SCB is the northern extent of their typical geographic range with peak abundance occurring during May-October, largely correlated with sea-surface temperatures. Further, analysis of fisheries-dependent data suggests that some of the largest (≥13 kg) individuals inhabit near-shore waters of the northern SCB year-round. Taken in sum, these observations suggest a well-structured pattern of space use within this species based upon physiological constraints and ontogenetic movements.
Results/Conclusions
To examine the spatial and temporal trends in the southern California yellowtail fishery, all instances of recreational yellowtail capture in southern California between 1936-2013 were retrieved from existing fishery databases (MRFSS, CRFS, CPFV logbook), and analyzed by size, season, location, and sea-surface temperature. Catch was bi-modally distributed with peaks at both immature and mature sizes, larger fish were caught inshore (<3 mi) while smaller fish were predominantly caught offshore (>3 mi). These trends varied predictably depending on season. Additionally, fish caught during winter months were significantly larger than those caught during the remainder of the year.
This defined spatial and temporal size segregation provided the motivation for a comprehensive tagging program within the southern SCB. Currently, the recapture rate stands at 21%, with time at liberty for tagged fish ranging from 24 hours to 18 months and recapture distance from 3-40km. Smaller fish showed higher vagility while larger fish demonstrated higher site-fidelity. These results suggest a strong pattern of shifting space use (both location and mobility) with age, revealing novel evidence of ontogenetic changes in movement for a coastal marine fish.
This work represents the first examination of both fisheries data and regional/local movements for California yellowtail since the 1950’s.