Southern California Bight Research Articles

Revisiting the life history of yellowtail jack (Seriola dorsalis) in the Southern California Bight: new evidence for ontogenetic habitat shifts and regional differences in a changing environment: Suppl. fig. 2

Revisiting the life history of yellowtail jack (Seriola dorsalis) in the Southern California Bight: new evidence for ontogenetic habitat shifts and regional differences in a changing environment: Suppl. fig. 2

Revisiting the life history of yellowtail jack (Seriola dorsalis) in the Southern California Bight: new evidence for ontogenetic habitat shifts and regional differences in a changing environment

Revisiting the life history of yellowtail jack (Seriola dorsalis) in the Southern California Bight: new evidence for ontogenetic habitat shifts and regional differences in a changing environment

Revisiting the life history of yellowtail jack (Seriola dorsalis) in the Southern California Bight: new evidence for ontogenetic habitat shifts and regional differences in a changing environment: Suppl. table

Revisiting the life history of yellowtail jack (Seriola dorsalis) in the Southern California Bight: new evidence for ontogenetic habitat shifts and regional differences in a changing environment: Suppl. table

Revisiting the life history of yellowtail jack (Seriola dorsalis) in the Southern California Bight: new evidence for ontogenetic habitat shifts and regional differences in a changing environment: Suppl. fig. 1

Revisiting the life history of yellowtail jack (Seriola dorsalis) in the Southern California Bight: new evidence for ontogenetic habitat shifts and regional differences in a changing environment: Suppl. fig. 1

Environmental drivers of population variability in colony‐forming marine diatoms

AbstractMany aquatic microbes form colonies, yet little is known about their abundance and fitness relative to single‐celled taxa. The formation of diatom chains, in particular, has implications for diatom growth, survival, and carbon transfer. Here, we utilize an autonomous underwater microscope, combined with traditional microscopy, to develop a novel, multiyear record of the abundance of single‐cell and colony‐forming diatoms at Scripps Pier, a coastal location in the Southern California Bight. The total abundance of diatoms was lower during the warmer and more stratified conditions from 2015 to early 2016, but increased in cooler and less stratified conditions in mid‐2016 to late 2017. Diatom blooms were dominated by chain‐forming taxa, whereas solitary diatoms prevailed during low‐biomass conditions. The abundance of dinoflagellates, some of which are important diatom predators, is highest when colonies (chains) are most abundant. These observations of the diatom assemblage are consistent with a trade‐off between resource acquisition and predator defenses. Solitary diatom cells dominated during conditions with weak nutrient supply because they have a greater diffusive catchment area per cell in comparison to cells living in colonies. In contrast, during bloom conditions when nutrient supply is high and predators are abundant, forming a colony may reduce predation losses to quickly growing microzooplankton predators, and afford chains a higher fitness despite the costs of sharing resources with neighboring cells. These results highlight the contrasting ecology of single‐cell and chain‐forming diatoms, and the need to differentiate them in monitoring campaigns and ecological models.

Contextualizing Marine Heatwaves in the Southern California Bight Under Anthropogenic Climate Change

AbstractIn early August 2018, record‐high sea surface temperatures were recorded in the 102 year old Scripps Institution of Oceanography daily temperature time series (SIOT) at La Jolla, CA, USA. The previous record of 25.8 °C, set in July 1931, was broken four times over 9 days, peaking at 26.4 °C on 9 August 2018. Optimum Interpolation Sea Surface Temperature data suggest that the marine heatwave (MHW) manifested in the northern half of the Baja California Peninsula, tapering off into the Southern California Bight. Here we use the Optimum Interpolation Sea Surface Temperature data to categorize this MHW as severe with relatively high maximum intensity (3.9 °C) and long duration (44 days) when compared to other events in the time series. Glider profiles show that the thermal anomaly was largest near the surface and extended to at least 100 m depth. By detrending the SIOT to remove the long‐term anthropogenic climate signal and comparing the resulting data set to the unadjusted, we contextualize this MHW with respect to the entire time series and demonstrate that the long‐term trend played a crucial role in amplifying the intensity and duration of the MHW. In this case, the anthropogenic warming signal in the SIOT accounts for an additional 19 MHW days (from 24 to 43) and an increase in cumulative intensity of 56.8 °C (from 83.1 to 139.9).

Volume and Heat Budgets in the Coastal California Current System: Means, Annual Cycles, and Interannual Anomalies of 2014–16

AbstractThe data-assimilating California State Estimate (CASE) enables the explicit evaluation of spatiotemporally varying volume and heat budgets in the coastal California Current System (CCS). An analysis of over 10 years of CASE model output (2007–17) diagnoses the physical drivers of the CCS mean state, annual cycles, and the 2014–16 temperature anomalies associated with a marine heat wave and an El Niño event. The largest terms in the mean mixed layer (from−50 to 0 m) volume budgets are upward vertical transport at the coast and offshore-flowing ageostrophic Ekman transport at the surface, the two branches of the coastal upwelling overturning cell. Contributions from onshore geostrophic flow in the Southern California Bight and alongshore geostrophic convergence in the central CCS balance the mean volume budgets. The depth-dependent annual cycle of vertical velocity exhibits the strongest upward velocity between −40- and −30-m depth in April. Interannual volume budgets show that over 50% of the 2013.5–16.5 time period experienced downwelling anomalies, which were balanced predominantly by alongshore transport convergence and, less often, by onshore transport anomalies. Mixed layer temperature anomalies persisted for the entirety of 2014–16, reaching a maximum of +3° in October 2015. The mixed layer heat budget shows that intermittent high air–sea heat flux anomalies and alongshore and vertical heat advection anomalies all contributed to warming during 2014–16. A subsurface (from −210 to −100 m) heat budget reveals that in September 2015 anomalous poleward heat advection into the Southern California Bight by the California Undercurrent caused deeper warming during the 2015/16 El Niño.

Evidence of changes in sedimentation rate and sediment fabric in a low-oxygen setting: Santa Monica Basin, CA

Abstract. The Southern California Bight is adjacent to one of the world's largest urban areas, Los Angeles. As a consequence, anthropogenic impacts could disrupt local marine ecosystems due to municipal and industrial waste discharge, pollution, flood control measures, and global warming. Santa Monica Basin (SMB), due to its unique setting in a low-oxygen and high-sedimentation environment, can provide an excellent sedimentary paleorecord of these anthropogenic changes. This study examined 10 sediment cores, collected from different parts of the SMB between spring and summer 2016, and compared them to existing cores in order to document changes in sedimentary dynamics during the last 250 years, with an emphasis on the last 40 years. The 210Pb-based mass accumulation rates (MARs) for the deepest and lowest oxygen-containing parts of the SMB basin (900–910 m) have been remarkably consistent during the past century, averaging 17.1±0.6 mg cm−2 yr−1. At slightly shallower sites (870–900 m), accumulation rates showed more variation but yield the same accumulation rate, 17.9±1.9 mg cm−2 yr−1. Excess 210Pb sedimentation rates were consistent with rates established using bomb test 137Cs profiles. We also examined 14C profiles from two cores collected in the deepest part of the SMB, where fine laminations are present up to about 450 yr BP. These data indicate that the MAR was slower prior to ∼1900 CE (rates obtained were 9 and 12 mg cm−2 yr−1). The δ13Corg profiles show a relatively constant value where laminations are present, suggesting that the change in sediment accumulation rate is not accompanied by a change in organic carbon sources to the basin. The increase in sedimentation rate towards the Recent occurs at about the time previous studies predicted an increase in siltation and the demise of a shelly shelf benthic fauna on the SMB shelf. X-radiographs show finely laminated sediments in the deepest part of the basin only, with centimeter-scale layering of sediments or no layering whatsoever in shallower parts of the SMB basin. The absence of finely laminated sediments in cores MUC 10 (893 m) and MUC 3 (777 m) suggests that the rate at which anoxia is spreading has not increased appreciably since cores were last analyzed in the 1980s. Based on core top data collected during the past half century, sedimentary dynamics within SMB have changed minimally during the last 40 years. Specifically, mass accumulation rates, laminated sediment fabric, extent of bioturbation and % Corg have not changed. The only parameter that appeared to have changed in the last 450 years was the MAR, with an apparent > 50 % increase occurring between ∼1850 CE and the early 1900s. The post-1900 CE constancy of sedimentation through a period of massive urbanization in Los Angeles is surprising.

Dynamic spawning patterns in the California market squid (Doryteuthis opalescens) inferred through paralarval observation in the Southern California Bight, 2012–2019

AbstractThe California market squid is ecologically and economically important to the California Current Ecosystem and coastal communities. However, the population undergoes periodic and large‐scale fluctuations on the order of magnitudes, largely as a result of warm ocean temperature and reduced ocean productivity related to cycles in El Niño Southern Oscillation. These fluctuations can lead to cascading trophic effects on the ecosystem, market uncertainty, and substantial revenue losses for fishing communities. In order to investigate the role that spawning behavior may play in mitigating the detrimental environmental effects on the population as well as allowing the species to capitalize during favorable ocean conditions, surveys for market squid paralarvae were conducted three times per hatching season from 2012 to 2019. The specific objectives were to (a) assess whether there was a large‐scale synchronous peak in paralarval abundance each season, (b) investigate whether market squid paralarvae were found at certain locations in similar abundances throughout the duration of a hatching season, and (c) to understand the influence of oceanographic parameters, such as zooplankton availability, sea surface temperature, and chl‐a on paralarvae abundance during each hatching season. Adaptable spawning strategies that varied over time were observed. Market squid displayed large‐scale synchronous spawning during cool and productive oceanographic conditions; protracted spawning was observed during warm and oligotrophic conditions. No overall site fidelity was observed across all effort, but during two seasons where habitat compression was possible, market squid consistently spawned in certain areas. Generalized additive models were used to explore the effects of a small set of oceanographic variables on paralarval density on a seasonal basis. Sea surface temperature and geographic variables were generally the most important variables. These findings indicate that market squid spawning behaviors and habitat are adaptable and dependent on oceanography and population density.

Common thresher shark Alopias vulpinus movement: Bayesian inference on a data-limited species

Within the fields of biology and ecology, animal movement is arguably one of the most basic, and yet, often one of the most difficult areas of study. Where and why animals migrate, and what patterns can be derived from individual movements in order to make population-level inferences are key areas when attempting to define basic population dynamics. These questions are of equal interest to biologists and managers, with many species assessments identifying improvements in the understanding of population-level movement as a key research need. We aimed to improve our understanding of population level movement for common thresher sharksAlopias vulpinusby leveraging the largest satellite tagging dataset available for this species. Using a Bayesian approach specifically designed to address population-level questions with sparse telemetry data, we identified thatA. vulpinusoff the west coast of North America are partial migrators which conditionally migrate, based on a combination of fixed intrinsic states (size, sex) and variable extrinsic states (e.g. season, environment). Waters of the Southern California Bight were identified as an area where, seasonally, a large variety of sizes ofA. vulpinuscan be found. While smaller juveniles can be found throughout the year, larger sub-adults and adults often move out of the Bight during certain seasons (spring and winter). Knowledge of howA. vulpinusdistribute along the coast, and that season, size, and to some extent sex, play important roles in where and what type of animals are likely to be found, are key pieces of information when attempting to accurately characterize basic biological parameters like age, growth, and reproduction, as well as understanding the effects of variable fishing pressures across the species’ range.

Impacts of the non-native alga Sargassum horneri on benthic community production in a California kelp forest

The arrival of Sargassum horneri throughout the Southern California Bight and the Baja Peninsula has raised concern regarding kelp forest resilience and ecosystem function following the invasion of this non-native species. To understand how S. horneri impacts native algal abundance and community production, we removed S. horneri from experimental plots over a period of 11 mo. We measured impacts on native algal communities and community productivity using SCUBA surveys and benthic chambers equipped with oxygen, temperature, and light sensors. We observed a nearly 4-fold increase in recruitment of Macrocystis pyrifera and a 9-fold increase in adult M. pyrifera stipe density in S. horneri removal plots, but no discernable changes in net community production among treatments. We found ephemeral increases in gross community production and community respiration in the non-removal plots that coincided with periods of peak S. horneri biomass. To understand the temporal dynamics of community production, we deployed benthic chambers across a rocky reef dominated by S. horneri. Here, temporal variation in community production was most strongly related to corresponding variation in water temperature and changes in S. horneri biomass related to its annual lifecycle. Overall, our study indicates that S. horneri presence contributed to ephemeral increases in gross community production and community respiration, but it did not affect net community production. Moreover, S. horneri removal can lead to increases in native algal abundances given favorable abiotic conditions. We suggest that S. horneri thrives in a disturbed ecosystem rather than being a driver of ecosystem change.

Physical and Biogeochemical Factors Driving Spatially Heterogeneous Phytoplankton Blooms in Nearshore Waters of Santa Monica Bay, USA

Phytoplankton blooms in nearshore waters are difficult to predict using only biogeochemical factors known to control phytoplankton growth, yet the need to understand these events continues to grow with expanding harmful algal bloom (HAB) events. The present study investigated the spatial and temporal dynamics of phytoplankton blooms and their drivers in King Harbor, a harbor in Santa Monica Bay in the Southern California Bight. High-frequency sensor measurements of environmental variables and biomass and discrete sampling of phytoplankton community composition and nutrients over an annual cycle were obtained. Eleven distinct bloom events, nine of which were numerically dominated by dinoflagellates, were identified over the study period. Results from both regression-based and time series analyses show that these blooms were correlated with increased temperature, changes in nutrient concentrations, and decreased tidally driven mixing, revealing an opportunity for bloom initiation close to neap tides. Predictors of chlorophyll biomass and environmental factors that explained differences in microplankton community structure differed between the two basins of King Harbor, despite their close and connected nature. Biomass and HAB taxa abundances in the harbor were significantly correlated with those in Santa Monica Bay with a 1-week lag in the harbor data, suggesting possible onshore transport of organisms into the harbor. The results of this study quantify the significant influence of tidal cycle as a physical process operating locally and at timescales of hours to days and provide evidence for a high degree of spatial heterogeneity in bloom dynamics in nearshore environments.

The Importance of Remote Forcing for Regional Modeling of Internal Waves

AbstractRegional ocean general circulation models are generally forced at the boundaries by mesoscale ocean dynamics and barotropic tides. In this work we provide evidence that remotely forced internal waves can be a significant source of energy for the dynamics. We compare global and regional model solutions within the California Current System. Both models have similar inputs, forcings, and identical grids and numerics. The global model has a steric height power spectrum consistent with mooring observations at superinertial frequencies, while the regional model spectrum is weaker. The regional model also has less sea surface height variance at high wavenumber than the global model. The vertical velocity variance is significantly larger in the global model, except in the sheltered Southern California Bight. While the regional model has roughly equal high‐pass baroclinic and barotropic kinetic energy levels, the global model high‐pass baroclinic kinetic energy is 28% (0.39 PJ) greater than the barotropic energy. An internal wave energy flux analysis reveals that the regional model domain boundaries act as a sink of 183 MW, while in the global model the analysis domain boundaries act as a source of 539 MW. This 722 MW difference can account for the relative increase of 0.39 PJ high‐pass baroclinic energy in the global model, assuming a baroclinic kinetic energy dissipation time in the domain of approximately 6.3 days. The results here imply that most regional ocean models will need to account for internal wave boundary fluxes in order to reproduce the observed internal wave continuum spectrum.

Sea Surface Temperature Imagery Elucidates Spatiotemporal Nutrient Patterns for Offshore Kelp Aquaculture Siting in the Southern California Bight

Offshore aquaculture of giant kelp (Macrocystis pyrifera) has been proposed by the US Department of Energy for large scale biofuel production along the west coast of the California. The Southern Californian Bight provides an ideal area for offshore kelp aquaculture as the upwelling and advection of cool, nutrient-rich waters supports the growth of vast native giant kelp populations. However, concentrations of nutrients vary greatly across space, can be limiting for kelp growth over seasonal to interannual time scales, and inputs of nutrients to surface waters may be subject to local circulation processes. Therefore, it is important to understand both the spatiotemporal variability of seawater nitrate concentrations and the appropriate scale of observation in order for offshore kelp aquaculture to be successful. Here, we use a combination of satellite sea surface temperature imagery, in situ measurements, and modeling to determine seawater nitrate fields across multiple spatial and temporal scales. We then combine this information with known giant kelp physiological traits to develop a Kelp Stress Index for the optimal siting of offshore kelp aquaculture over seasonal to decadal scales. Temperature to nitrate relationships were determined from in situ measurements using generalized additive models and validated with buoy data. Summer and winter relationships were significantly different, and satellite-derived products compared well to buoy validations. Surface nitrate patterns, as derived from satellite temperature products, reveal the spatial variability in nitrate concentrations and indicate areas that that may cause nutrient stress seasonally and during the negative phase of the North Pacific Gyre Oscillation. As the spatial scale of the surface nitrate product decreased, the negative bias increased and fine scale spatial variability was lost. Similarly, the averaging of daily nitrate concentration determinations over longer time scales increased the negative bias. We found that daily, 1 km spatial resolution nitrate products were most sufficient for identifying localized upwelling and areas of consistently high surface nitrate concentrations, and that areas in the northern and western-most portions of the Southern California Bight are the most suitable for sustained offshore kelp aquaculture.

Insights into the horizontal movements, migration patterns, and stock affiliation of California swordfish

AbstractThis study reports on the horizontal movements of swordfish (Xiphias gladius L.) tagged during deep‐set fishery trials off the California coastline. Position estimates from several electronic tag types were used to better understand swordfish stock structure and regional affiliation with current boundary hypotheses used to manage swordfish in the eastern north Pacific. Swordfish were outfitted with (a) satellite‐linked mark–recapture tags (n = 66), (b) electronic data storage tags that were recaptured (n = 16), (c) fin‐mounted Argos transmitters (n = 6), and (d) satellite‐linked archival tags (n = 4). Twenty‐six percent of tagged swordfish reported close to (<225 km) their deployment location within the southern California Bight (SCB). Of the 50 swordfish that moved outside the SCB, 76% exhibited affiliation to the Eastern Pacific Ocean (EPO) management unit, 20% moved into the Western and Central North Pacific (WCNP) and 4% spent time within both the EPO and WCNP boundaries. Mean displacement between deployment and reporting locations was 1,250 ± 1,375 km, with daily rates of movement up to 55 km/day. Seasonal migrations ranged from the equator (0.8°N.132.4°W) to the Hawaiian Islands (17.0°N/154.2°W), with multiple individuals returning to the initial tagging locations the subsequent season. Seasonal site fidelity exhibited by several individuals highlights the importance of the SCB foraging grounds. While no evidence of trans‐equatorial or trans‐Pacific crossing was documented, extensive movements validate the highly migratory nature of California swordfish and support the need for future inclusion of spatial distribution data in management. Findings suggest that SCB swordfish may exhibit a higher level of EPO connectivity than previously proposed.

Secondary Production of Kelp Bass Paralabrax clathratus in Relation to Coastal Eelgrass Zostera marina Habitat in a Southern California Marine Protected Area

Seagrasses are an important refuge for fishes and provide ecosystem services worldwide. Along the Pacific Coast, however, quantitative assessments of the ecological role of seagrass habitats with limited anthropogenic impacts are lacking despite their value to resource management. To address these issues, the ecological function of the eelgrass Zostera marina Linnaeus in a protected area off Santa Catalina Island, California, USA was quantified using estimates of secondary production in the kelp bass Paralabrax clathratus (Girard, 1854). Monthly assessments of Zostera structural complexity, as well as the size and abundance of juvenile kelp bass were used to establish a baseline of fish biomass and recruitment associated with Zostera habitat. The greatest number of kelp bass was recorded in the summer and fall months and the fewest during the winter and spring. Secondary production in kelp bass (0.1 to 0.59 g m–2 mo–1) followed monthly changes in Zostera habitat structure throughout the 24-month study period. Seasonal changes in the structural complexity of coastal Zostera beds may influence the flow of energy to adjacent reef environments through the transfer of fish biomass. These findings help define the potential role of Zostera habitat within the larger context of nearshore coastal ecosystems in the Southern California Bight.

Pre‐closure fishing pressure predicts effects of marine protected areas

Abstract Marine protected areas (MPAs) can be effective tools for marine resource management. However, despite evidence of the positive effects of MPAs, such as increases in body sizes of organisms targeted by fisheries, there is often heterogeneity in biological outcomes among them. Because fishing can drastically impact fish populations, the goal of this study was to determine if the levels of exploitation prior to protection could predict variation in the magnitude of MPA effects. Using a diver‐operated stereo–video camera system, we compared sizes of fishes targeted by anglers within seven MPAs spanning the Southern California Bight to nearby comparison areas (non‐MPAs). We used fine‐scale data on pre‐closure fishing pressure to test responses of fishes to protection along a gradient of exploitation. Fish size responded to protection in proportion to pre‐closure fishing pressure, with MPAs in areas with high pre‐closure fishing having greater responses in average lengths and size distributions than those in areas with low fishing pressure. This response was evident in species heavily targeted by recreational fishing, but not in species that were not targeted in fisheries. Synthesis and applications. Pre‐closure fishing pressure of an area can impact the efficacy of MPAs, and, when available, should be considered when predicting and evaluating MPA performance. Prioritizing heavily exploited areas for protection when implementing spatial management tools could maximize ecological outcomes.

The abundance and habitat use of demersal fishes on a rocky offshore bank using the ROPOS remotely operated vehicle

Offshore rocky banks are ecologically important refuge habitats for a number of U.S. commercial groundfish species. However, they are challenging to survey, and data on the abundance and ecology of fish populations at deep banks are limited. We used the remotely operated vehicle ROPOS to carry out visual surveys at two sites on Cherry Bank in the Southern California Bight, eastern Pacific Ocean. We observed differences in fish assemblages related to depth and habitat type and found that rockfishes (Sebastes spp) made up 65% of fishes recorded. Rockfishes and combfish (Zaniolepis spp) were associated with relatively shallow areas with hard substrate whereas flatfishes (Pleuronectiformes) and poachers (Agonidae) were found on unconsolidated sediments. Thornyheads (Sebastolobus spp) and hagfishes (Myxinidae) mainly occurred in areas of patchy habitat. Habitat and depth explained 52% of the variation in fish assemblages between transects with habitat explaining a greater proportion of the variation than depth. We observed large differences in the number of juvenile rockfishes and Sebastomus rockfishes between study sites with hard substrates and also had higher abundances of juvenile rockfishes versus sites characterized by mixed substrates. With the exception of unidentified Sebastomus, the current design had relatively low power to reliably detect observed differences for most taxa, so we report the number of additional transects that would be required to detect a 50% increase in densities. These data provide a baseline on groundfish densities and habitat associations at Cherry Bank and key information for the design of future work including Bayesian approaches to estimating coast-wide abundance.

Night and Day: Diel Differences in Ship Strike Risk for Fin Whales (Balaenoptera physalus) in the California Current System

Collisions with ships (ship strikes) are a pressing conservation concern for fin whales (Balaenoptera physalus) along western North America. Fin whales exhibit strong diel patterns in dive behavior, remaining near the surface for most of the night, but how this behavior affects ship-strike risk is unknown. We combined diel patterns of surface use, habitat suitability predictions, and ship traffic data to evaluate spatial and temporal trends in ship-strike risk to fin whales of the California Current System (CCS). We tested a range of surface-use scenarios and found that both increased use of the upper water column and increased ship traffic contribute to elevated ship-strike risk at night. Lengthening nights elevate risk during winter throughout the CCS, though the Southern California Bight experienced consistently high risk both day and night year-round. Within designated shipping lanes, total annual nighttime strike risk was twice daytime risk. Avoidance probability models based on ship speed were used to compare the potential efficacy of speed restrictions at various scales. Speed reductions within lanes may be an efficient remediation, but they would address only a small fraction (13%) of overall ship-strike risk. Additional speed restrictions in the approaches to lanes would more effectively reduce overall risk.

Estimating habitat-specific abundance and behavior of several groundfishes using stationary stereo still cameras in the southern California Bight

The increasing use of underwater cameras to estimate fish abundance often does not account for the behavior of target species. These behaviors can affect detectability of fish and bias density estimates. This study estimated abundance and behavior of several rockfishes (Sebastes spp.) and lingcod (Ophiodon elongatus) at Footprint Bank, a small offshore bank using images from randomly deployed stationary cameras. Deployments collected images at 30-second intervals over ∼24 h periods to examine the behaviors of rockfish that might impact abundance estimates. The results showed that time of day and tidal change had a significant effect on the probability of presence, estimated abundance and species composition of fish, with densities highest for most species during daylight hours. The time elapsed since camera deployment did not have a significant effect on fish density. Fish density was significantly affected by habitat composition, an effect primarily driven by speckled rockfish (Sebastes ovalis) which exhibited a 5-fold increase in abundance in bedrock habitats. Speckled rockfish were the most abundant rockfish at depths less than 150 m, with an estimated abundance of 12,994 fish (SE = 6,722) on Footprint Bank. The abundance estimates and coefficients of variation were comparable to surveys conducted in 2011 and 2012 using remotely operated vehicles (ROVs) and manned submersibles. The implications of this study are that habitat and behavior as well as timing of the survey (day/night) are important considerations determining the perceived density of fishes from underwater image surveys.