Jeremy T. Claisse

Oil platforms off California are among the most productive marine fish habitats globally

Significance Secondary production is the formation of new animal biomass from growth for all individuals in a given area during some period of time. It can be a powerful tool for evaluating ecosystem function because it incorporates multiple characteristics of a population or community of organisms such as density, body size, growth, and survivorship into a single metric. Here, we find that fish communities living on the complex hardscape habitat created throughout the water column by the structure of oil and gas platforms off California have the highest secondary production per unit area of seafloor of any marine ecosystem for which similar estimates exist. Secondary (i.e., heterotrophic or animal) production is a main pathway of energy flow through an ecosystem as it makes energy available to consumers, including humans. Its estimation can play a valuable role in the examination of linkages between ecosystem functions and services. We found that oil and gas platforms off the coast of California have the highest secondary fish production per unit area of seafloor of any marine habitat that has been studied, about an order of magnitude higher than fish communities from other marine ecosystems. Most previous estimates have come from estuarine environments, generally regarded as one of the most productive ecosystems globally. High rates of fish production on these platforms ultimately result from high levels of recruitment and the subsequent growth of primarily rockfish (genus Sebastes) larvae and pelagic juveniles to the substantial amount of complex hardscape habitat created by the platform structure distributed throughout the water column. The platforms have a high ratio of structural surface area to seafloor surface area, resulting in large amounts of habitat for juvenile and adult demersal fishes over a relatively small footprint of seafloor. Understanding the biological implications of these structures will inform policy related to the decommissioning of existing (e.g., oil and gas platforms) and implementation of emerging (e.g., wind, marine hydrokinetic) energy technologies.

Lunar and seasonal patterns in fecundity of an indeterminate, multiple-spawning surgeonfish, the yellow tang Zebrasoma flavescens.

Reproduction was investigated in relation to lunar and annual cycles in a population of yellow tang Zebrasoma flavescens, a popular aquarium species commercially harvested in Hawaii. Lunar periodicity was determined to be an inherent characteristic of reproduction; peaks in mean daily egg production, female gonado-somatic index (I(G)) and the fraction of females with eggs were observed at the full moon of each sampled month. An increase in the fraction of late-stage vitellogenic oocytes within the ovaries was also observed at the full moon. Reproductive effort peaked in the late spring and summer as indicated by high values of mean daily egg production, female I(G) and the recorded incidence of females spawning for at least two consecutive days. Mean daily egg production and I(G) of monthly samples were lowest in November to February, although some level of egg production continued throughout the year. Large individual variation in batch fecundity was observed, with a range from 44 to > 24,000 eggs per female produced on a single sampling date. Smaller females, 80-120 mm standard length (L(S)), produced limited numbers of eggs, while females > or = 120 mm L(S) were capable of maximal egg production (> 20,000 eggs per batch). In contrast to trends observed in many fish species, no significant relationship between batch fecundity and adult L(S) > 120 mm was observed in female Z. flavescens. An estimate of annual fecundity (mean +/-S.E. 1,055,628 +/- 120,596 eggs) was also generated using a simple model of the lunar variability in egg production. This study illustrates the importance of accounting for potential variation in egg production over time, especially with respect to diel and lunar cycles, in the design of reproductive studies of multiple-spawning fishes. Greater insight into the environmental factors that regulate reproductive activity may be gained by determining the relative reproductive investment allocated at each spawning event. The ability to estimate annual fecundity for more multiple-spawning species will facilitate examination of the effects of fishing on the reproductive characteristics of these populations and permit examination of life-history evolution across a broader suite of fishes.

Kelp forest habitat restoration has the potential to increase sea urchin gonad biomass

When taking an ecosystem-based approach to marine resource management, managers may be able to implement a combination of management tools in order to mitigate the socioeconomic impacts of implementing any one in isolation, while providing greater overall ecological benefits. The harvest of Strongylocentrotus franciscanus (red sea urchin) for their gonads is one of the most important commercial fisheries in California. However, in some locations, high densities of the unfished Strongylocentrotus purpuratus (purple sea urchin) can clear expanses of kelp forest resulting in “urchin barrens.” The lack of macroalgal food resources can result in reduced gonad production, making S. franciscanus within barrens less valuable to a fishery. We investigated the potential of kelp forest habitat restoration, which may be achievable primarily by removing S. purpuratus from barrens, to positively impact the local S. franciscanus fishery and offset the losses in fishing grounds within recently established MPAs in our study area. Generalized linear modeling of the relationship between gonad weight and length (test diameter) demonstrated clear size-specific differences in gonad production between urchins collected in barrens and kelp forests. These relationships varied over time, with the maximum observed mean gonad biomass at length being 484% greater in kelp forest than barren habitat for S. franciscanus just above the legal size limit. The variability in S. franciscanus density (5.2 times greater in urchin barrens), size structure (mean test diameters were approximately 50% greater in kelp forest) and gonad production were then incorporated using Monte Carlo simulations. Results indicated that restoration could potentially result in an 864% increase in S. franciscanus gonad biomass available to the fishery, and a 132% increase in reproductive potential per unit area of urchin barren restored to kelp forest. If all 36 ha of urchin barren habitat mapped outside of the new MPAs in the study area were restored, the increase in gonad biomass available to the fishery could potentially offset 52% of which is now protected within the 109 ha of rocky reef in the new MPAs. Kelp restoration has the potential to play a valuable role as one of many integrated tools in an ecosystem-based management approach.

Impacts from Partial Removal of Decommissioned Oil and Gas Platforms on Fish Biomass and Production on the Remaining Platform Structure and Surrounding Shell Mounds

When oil and gas platforms become obsolete they go through a decommissioning process. This may include partial removal (from the surface to 26 m depth) or complete removal of the platform structure. While complete removal would likely eliminate most of the existing fish biomass and associated secondary production, we find that the potential impacts of partial removal would likely be limited on all but one platform off the coast of California. On average 80% of fish biomass and 86% of secondary fish production would be retained after partial removal, with above 90% retention expected for both metrics on many platforms. Partial removal would likely result in the loss of fish biomass and production for species typically found residing in the shallow portions of the platform structure. However, these fishes generally represent a small proportion of the fishes associated with these platforms. More characteristic of platform fauna are the primarily deeper-dwelling rockfishes (genus Sebastes). “Shell mounds” are biogenic reefs that surround some of these platforms resulting from an accumulation of mollusk shells that have fallen from the shallow areas of the platforms mostly above the depth of partial removal. We found that shell mounds are moderately productive fish habitats, similar to or greater than natural rocky reefs in the region at comparable depths. The complexity and areal extent of these biogenic habitats, and the associated fish biomass and production, will likely be reduced after either partial or complete platform removal. Habitat augmentation by placing the partially removed platform superstructure or some other additional habitat enrichment material (e.g., rock boulders) on the seafloor adjacent to the base of partially removed platforms provides additional options to enhance fish production, potentially mitigating reductions in shell mound habitat.

Using GIS mapping of the extent of nearshore rocky reefs to estimate the abundance and reproductive output of important fishery species.

Kelp Bass (Paralabrax clathratus) and California Sheephead (Semicossyphus pulcher) are economically and ecologically valuable rocky reef fishes in southern California, making them likely indicator species for evaluating resource management actions. Multiple spatial datasets, aerial and satellite photography, underwater observations and expert judgment were used to produce a comprehensive map of nearshore natural rocky reef habitat for the Santa Monica Bay region (California, USA). It was then used to examine the relative contribution of individual reefs to a regional estimate of abundance and reproductive potential of the focal species. For the reefs surveyed for fishes (i.e. 18 out of the 22 in the region, comprising 82% the natural rocky reef habitat <30 m depth, with a total area of 1850 ha), total abundance and annual egg production of California Sheephead were 451 thousand fish (95% CI: 369 to 533 thousand) and 203 billion eggs (95% CI: 135 to 272 billion). For Kelp Bass, estimates were 805 thousand fish (95% CI: 669 to 941thousand) and 512 billion eggs (95% CI: 414 to 610 billion). Size structure and reef area were key factors in reef-specific contributions to the regional egg production. The size structures of both species illustrated impacts from fishing, and results demonstrate the potential that relatively small increases in the proportion of large females on larger reefs could have on regional egg production. For California Sheephead, a substantial proportion of the regional egg production estimate (>30%) was produced from a relatively small proportion of the regional reef area (c. 10%). Natural nearshore rocky reefs make up only 11% of the area in the newly designated MPAs in this region, but results provide some optimism that regional fisheries could benefit through an increase in overall reproductive output, if adequate increases in size structure of targeted species are realized.

Morphometric Relationships of Marine Fishes Common to Central California and the Southern California Bight

Chelsea M. Williams,* Jonathan P. Williams, Jeremy T. Claisse, Daniel J. Pondella II., Michael L. Domeier, and Laurel A. Zahn Vantuna Research Group, Department of Biology, Occidental College, 1600 Campus Road, Los Angeles, CA 90041, USA California Department of Fish and Wildlife, 1416 9 Street, 12 Floor, Sacramento, CA 95814, USA (Current affiliation) Marine Conservation Science Institute, 68-1825 Lina Poepoe Street, Waikoloa, HI 96738, USA

Patterns of Life History and Habitat Use of an Important Recreational Fishery Species, Spotfin Croaker, and Their Potential Fishery Implications

Abstract Spotfin croakers Roncador stearnsii, a prized recreational catch, were collected throughout the Southern California Bight, primarily as bycatch from a long-term, scientific gill-net collection effort. The maximum otolith-based age in the present study was 24 years—14 years greater than in a previous scale-based aging study. Multiple models were used to estimate mean length at age, including models that utilize larvae as well as juveniles and adults, and the model selection results suggest sexual dimorphism in growth patterns. The juvenile and adult catch per unit effort reflected a clear pattern of habitat selectivity, with fish strongly preferring soft-bottom habitats. Catches in rocky-reef areas were limited but tended to increase with water temperature. The data also suggest that spotfin croakers segregate themselves sexually during the spawning season, when recreational fishing from jetties will target males and fish caught in bays and estuaries are more likely to be spawning females. These results provide further evidence for the importance of protection and restoration efforts for estuaries and bays along this well-developed coastline. The growth of larvae captured in plankton tows in July and September 2004 was substantially faster than that of larvae sampled in May, which coincided with warmer sea surface temperatures, highlighting a potentially important relationship relating temperature (and therefore geography) and settlement success.

Can nearshore seabirds detect variability in juvenile fish distribution at scales relevant to managing marine protected areas

Funding information California Sea Grant through the California Marine Protected Areas Baseline Program; David and Lucille Packard Foundation; University of Southern California (USC) Sea Grant, Grant/Award Number: 10-069; California Coastal Conservancy; National Oceanic and Atmospheric Administration (NOAA); Restoration Center; Montrose Settlements Restoration Program; The Bay Foundation Abstract Juvenile recruitment is an important determinant of change within marine protected areas (MPAs). Understanding spatiotemporal variability in recruitment rates will help managers set realistic expectations for rates of population and community level change within individual MPAs. Here we ask whether seabird foraging rates can be used as a proxy for juvenile fish recruitment at spatial scales relevant to MPA management. We investigated the foraging rates of six piscivorous seabirds inside and outside of three island and four mainland MPAs in Southern California and compared these rates to estimates of juvenile fish density from kelp forest surveys conducted at the same sites during the same 2 years (2012 and 2013). Juvenile fish communities at island and mainland sites were dominated by three families, Embiotocidae, Labridae and Pomacentridae, in both years. Additionally, there was an influx of youngoftheyear rockfishes (family Sebastidae) at most sites in 2013. Seabird and fish distributions were similar at the regional (approximately 15–30 km) scale, but less similar at the sitespecific scale. Sitespecific differences reflected differences in the diet and foraging habits of individual seabird species. While fish surveys were specific to the kelp forest habitat, seabirds were sampling multiple habitats (i.e. multiple water depths over multiple bottom substrates) within a given site. Our results suggest that integrating seabird data with data on juvenile fish abundance can produce a more holistic index to proxy spatiotemporal variability in juvenile fish recruitment. In other words, seabird studies can provide additional information not captured by fish surveys and help resource managers better understand local patterns of fish recruitment at the community level. This will help resource managers establish realistic expectations for how quickly fish populations should change within individual MPAs.