Using California Halibut Abundance and Behavior to Evaluate Ecosystem Recovery In a Restored Southern California Estuary

The California halibut, Paralichthys californicus, is an economically important teleost that utilizes estuaries as juvenile nursery habitat.  California has lost over 90% of its coastal estuaries and wetlands through development, which is thought to have impacted a number of coastal fishes in southern California.  Acoustic telemetry was used to identify patterns of residency and fine-scale habitat use of subadult California halibut (mean TL 40 ± 11.6 cm, mean ± SD) within the Huntington Beach Wetlands (HBW) to examine how fish were using various parts of the differentially restored estuary.  No tagged fish (n = 9) were found to leave the HBW during the 10-day active tracking observation period, which were spread across seasons. Halibut showed a mean home range size of 11,833 m² (range = 1,712 – 28,667 m²) and a mean core habitat use of 1,826 m² (range= 86—12,212 m²); however, there is no correlation between home range size and fish size.  Halibut showed a high degree of site fidelity indicated by high overlap in activity space over time.  Halibut used tidal channel habitat (vs. marsh creek habitat) 100% of the time although it constitutes only 54% of the total available habitat.  While in channel habitat, individuals utilized shell hash and ecotone habitat (sand/ eelgrass (Zostera marina)) disproportionately more than its availability within the HBW.  Halibut which were translocated to marsh creek habitat returned to channel habitat within 12 hrs of release where they displayed movement behavior similar to non-translocated individuals.  Fish abundance surveys throughout the HBW suggest there is size segregation for this species, with smaller fish found throughout the marsh creeks and channel habitat but larger individuals found primarily in channel habitat.  Findings suggest restored estuaries/marshes containing channel-like habitat with high water flow and eelgrass ecotone may support more juvenile and sub-adult halibut over at least short periods of time (~ 1 month).  Ongoing passive tracking of halibut tagged with long-life coded transmitters in the HBW have provided information on long-term site fidelity, indicating that residency within the HBW may be seasonally variable and last as long as 5 months. Preliminary results suggest that larger fish prefer to use more established parts of the restored estuary but smaller halibut are using the newly restored portions of the HBW, which may be attributed to differential habitat selection or predator avoidance.