Underwater Video Camera Research Articles

Temporal patterns of Pederson shrimp (Ancylomenes pedersoni Chace 1958) cleaning interactions on Caribbean coral reefs

Dozens of marine species have been identified as “cleaners” and many of these co-occur and have considerable overlap in clientele. Understanding the temporal patterns and processes of these cleaning symbioses can provide insight into differential service provision between cleaner species and the ultimate and proximate causes structuring these interactions. Considerable progress has been made in understanding the ecology and behavior of cleaner fish, yet little basic ecological and behavioral data exist for cleaner shrimp. We deployed remote underwater video cameras on coral reefs in the Bay Islands, Honduras, to explore temporal variation of cleaning interactions at Pederson shrimp (Ancylomenes pedersoni) stations. We recorded more than 650 individual cleaning interactions in over 190 h of video. We find no significant temporal variation in cleaning station usage patterns across 17 families of reef fish. Our findings are in contrast to previously published data for interactions of Caribbean cleaner gobies, which co-occur at the sites we studied and overlap significantly in client pool with A. pedersoni but which are most active at dawn. These data suggest that the services provided by cleaner shrimp and cleaner gobies, rather than client identity, independently structure these interactions and drive the discordance in usage patterns between cleaner type. We propose two non-exclusive hypotheses to explain the differences in the temporal patterns of activity between cleaner gobies and A. pedersoni: (1) the proximate causes driving fish visitation rate (e.g., parasite removal or tactile stimulation) to goby and shrimp stations differ, and (2) each cleaner type targets different ectoparasites that differ temporally in their diel infestation rate on reef fish. Our study provides an important rationale for pursuing these questions and broadens our understanding of cleaning services on Caribbean coral reefs.

Breast Support Garments are Ineffective at Reducing Breast Motion During an Aqua Aerobics Jumping Exercise.

The buoyant forces of water during aquatic exercise may provide a form of ‘natural’ breast support and help to minimise breast motion and alleviate exercise induced breast pain. Six larger-breasted females performed standing vertical land and water-based jumps, whilst wearing three breast support conditions. Underwater video cameras recorded the motion of the trunk and right breast. Trunk and relative breast kinematics were calculated as well as exercised induced breast pain scores. Key results showed that the swimsuit and sports bra were able to significantly reduce the superioinferior breast range of motion by 0.04 and 0.05 m, respectively, and peak velocity by 0.23 and 0.33 m/s, respectively, during land-based jumping when compared to the bare-breasted condition, but were ineffective at reducing breast kinematics during water-based jumping. Furthermore, the magnitude of the swimsuit superioinferior breast range of motion during water-based jumping was significantly greater than land-based jumping (0.13 m and 0.06 m), yet there were no significant differences in exercise induced breast pain, thus contradicting previously published relationships between these parameters on land. Furthermore, the addition of an external breast support garment was able to reduce breast kinematics on land but not in water, suggesting the swimsuit and sports bras were ineffective and improvements in swimwear breast support garments may help to reduce excessive breast motion during aqua aerobic jumping exercises.

Sessile and mobile components of a benthic ecosystem display mixed trends within a temperate marine reserve

Despite recent efforts to increase the global coverage of marine protected areas (MPAs), studies investigating the effectiveness of marine protected areas within temperate waters remain scarce. Furthermore, out of the few studies published on MPAs in temperate waters, the majority focus on specific ecological or fishery components rather than investigating the ecosystem as a whole. This study therefore investigated the dynamics of both benthic communities and fish populations within a recently established, fully protected marine reserve in Lamlash Bay, Isle of Arran, United Kingdom, over a four year period. A combination of photo and diver surveys revealed live maerl (Phymatolithon calcareum), macroalgae, sponges, hydroids, feather stars and eyelash worms (Myxicola infundibulum) to be significantly more abundant within the marine reserve than on surrounding fishing grounds. Likewise, the overall composition of epifaunal communities in and outside the reserve was significantly different. Both results are consistent with the hypothesis that protecting areas from fishing can encourage seafloor habitats to recover. In addition, the greater abundance of complex habitats within the reserve appeared to providing nursery habitat for juvenile cod (Gadus morhua) and scallops (Pecten maximus and Aequipecten opercularis). In contrast, there was little difference in the abundance of mobile benthic fauna, such as crabs and starfish, between the reserve and outside. Similarly, the use of baited underwater video cameras revealed no difference in the abundance and size of fish between the reserve and outside. Limited recovery of these ecosystem components may be due to the relatively small size (2.67 km2) and young age of the reserve (<5 years), both of which might have limited the extent of any benefits afforded to mobile fauna and fish communities. Overall, this study provides evidence that fully protected marine reserves can encourage seafloor habitats to recover, which in turn, can create a number of benefits that flow back to other species, including those of commercial importance.

Among-habitat algal selectivity by browsing herbivores on an inshore coral reef

Understanding how the impact of different herbivores varies spatially on coral reefs is important in qualifying the resistance of coral reefs to disturbance events and identifying the processes that structure algal communities. We used assays of six common macroalgae (Acanthophora spicifera, Caulerpa taxifolia, Galaxaura rugosa, Laurencia sp. Sargassum sp., and Turbinaria ornata) and remote underwater video cameras to quantify herbivory in two habitats (reef crest and slope) across multiple sites on Orpheus Island, Great Barrier Reef. Rates of herbivory varied among macroalgal taxa, habitats, and sites. Reductions in algal biomass were greatest for Sargassum sp. (36 % 4 h−1), intermediate for A. spicifera, Laurencia sp., C. taxifolia, and T. ornata (17–33 % 4 h−1) and lowest for G. rugosa (6 % 4 h−1). Overall, rates of herbivory were generally greater on the reef crest (30 % 4 h−1) than the reef slope (21 % 4 h−1). This difference in rates of herbivory coincided with a marked shift in the dominant herbivores between habitats. Kyphosus vaigiensis, despite only feeding on three species of macroalgae (Sargassum sp., T. ornata, and A. spicifera), was responsible for 34 % of all bites recorded on the reef crest yet did not take a single bite from algae on the reef slope. In contrast, Siganus doliatus took bites on every species of algae in both habitats, accounting for 40 % of bites on the reef crest and 74 % of all bites recorded on the reef slope. This difference in the number of macroalgal species targeted by herbivores and the habitat/s in which they feed adds another dimension of complexity to our understanding of coral reef herbivore dynamics.

Synchronous and Rhythmic Vocalizations and Correlated Underwater Behavior of Free-ranging Atlantic Spotted Dolphins (Stenella frontalis) and Bottlenose Dolphins (Tursiops truncatus) in the Bahamas

Since 1985 a resident community of Atlantic spotted dolphins (Stenella frontalis), and bottlenose dolphins (Tursiops truncatus), have been studied underwater in the Bahamas. Over 200 individuals of both species have been identified and observed over the years. Basic correlations with sound patterns and behavior such as whistles during contact/reunions and squawks during aggression have been reported. This paper describes a small subset of their vocal repertoire that involves synchronous/rhythmic sound production. Dolphin behavior was recorded underwater using underwater video cameras with hydrophone input. Vocalizations were correlated with basic underwater behavioral activity and analyzed using Raven 1.3. Spotted dolphins were observed using two types of synchronized vocalizations including synchronized squawks (burst pulsed vocalizations) and screams- (overlapping FM whistles) during intraspecific and interspecific aggression. Bottlenose dolphins used three types of synchronized vocalizations; whistles/buzz bouts, bray/buzz bouts, and buzz bouts during intraspecific aggression. Body postures were synchronous with physical movements and often mirrored the rhythm of the vocalizations. The intervals between highly synchronized vocalizations had small variance and created a rhythmic quality and cadence to the acoustic sequences. Three types of vocalizations had similar ratios of sound duration to the spacing between sounds (Screams, whistle/buzz bouts, and bray/buzz bouts). Temporal aspects of sequences of sound and postures may be important aspects of individual and group coordination and behavior in delphinids.

The efficiency of selection grids in perch pontoon traps

In commercial fishing, minimizing the bycatch of undersized fish or non-target species is highly beneficial, to avoid unnecessary fish mortality and to save time for the fishers. Two pontoon traps developed for perch fishing were equipped with size selection grids, and the efficiency with which under-sized fish could escape was tested. Average size of perch, roach, and whitefish was larger in traps with selection grids compared to in control traps without grids. Selection efficiencies using these comparisons were 82–86% for perch, 33% for whitefish and 100% for roach. The selection grids were filmed with an underwater video camera over the daily cycle, to estimate timing, and total number of exits from the traps. Selection efficiencies, calculated by extrapolating number of escapes observed to the total time of trap submergence, were 94–100% for perch and 100% for roach. The discrepancy in the selection efficiency estimates for perch probably depends on an uncertainty in the extrapolation, because of the variation in escape rate across time periods. Perch and roach differed in time of day for escapes. For perch most escapees was seen in the evening, and for roach most fish escaped at night, probably reflecting the general activity cycles of the two species. Over a fishing season, several thousands of fish would be able to escape from each trap, and an increase in the use of size selection grids could potentially be an efficient tool for fish population management.

Use of underwater video to assess freshwater fish populations in dense submersed aquatic vegetation

Underwater video cameras (UVC) provide a non-lethal technique to sample fish in dense submersed aquatic vegetation. Fish often inhabit densely vegetated areas, but deficiencies of most sampling gears bias relative abundance estimates that inform fisheries management. This study developed methods using UVC to estimate relative abundance in dense vegetation using three experimental ponds covered with surface-matted hydrilla (Hydrilla verticillata) stocked at different densities of Lepomis spp. and largemouth bass (Micropterus salmoides). We conducted UVC point counts over 13 weeks to measure relative fish abundance and occurrence from video analysis. Ponds were then drained to obtain true fish densities. In total, fish were detected in 55% of all counts and juvenile and adult Lepomis spp. and largemouth bass were enumerated. End-of-season true fish densities ranged across ponds (from 52 to 37000 fishha–1). Additionally, pond 2’s true density changed substantially from 370 to 12300 fishha–1. True population size was accurately reflected in differences in estimated relative abundances obtained from fish counts, as in pond 2 where mean fish counts increased from 0.10 in week 1 to 2.33 by week 13. Underwater video accurately and precisely quantified relative abundance at naturally-occurring fish densities, but this success was reduced at low densities.

Bay-scale assessment of eelgrass beds using sidescan and video

The assessment of the status of eelgrass (Zostera marina) beds at the bay-scale in turbid, shallow estuaries is problematic. The bay-scale assessment (i.e., tens of km) of eelgrass beds usually involves remote sensing methods such as aerial photography or satellite imagery. These methods can fail if the water column is turbid, as is the case for many shallow estuaries on Canada’s eastern seaboard. A novel towfish package was developed for the bay-scale assessment of eelgrass beds irrespective of water column turbidity. The towfish consisted of an underwater video camera with scaling lasers, sidescan sonar and a transponder-based positioning system. The towfish was deployed along predetermined transects in three northern New Brunswick estuaries. Maps were created of eelgrass cover and health (epiphyte load) and ancillary bottom features such as benthic algal growth, bacterial mats (Beggiatoa) and oysters. All three estuaries had accumulations of material reminiscent of the oomycete Leptomitus, although it was not positively identified in our study. Tabusintac held the most extensive eelgrass beds of the best health. Cocagne had the lowest scores for eelgrass health, while Bouctouche was slightly better. The towfish method proved to be cost effective and useful for the bay-scale assessment of eelgrass beds to sub-meter precision in real time.

Evaluation of WorldView-2 and acoustic remote sensing for mapping benthic habitats in temperate coastal Pacific waters

Maps of nearshore marine habitat are fundamental tools for the management and conservation of coastal ecosystems. While traditional field mapping techniques, such as towed video and diver surveys, are still commonly employed for generating highly detailed maps of seafloor habitat, acoustic and satellite remote sensing have proven to be efficient alternatives for generating habitat maps. To date remote sensing using satellite imagery has dominated mapping efforts over coral reefs and other tropical ecosystems with fewer studies applied in temperate marine regions where acoustic studies are more common. Few studies exist that have assessed the performance of high resolution satellite imagery in mapping seafloor habitat in temperate regions. This paper compares the efficacy of high resolution satellite imagery (WorldView-2) and a single-beam acoustic ground discrimination system (QTC View V) for mapping the distribution of submerged aquatic vegetation at a site within the Gwaii Haanas National Marine Conservation Area (GHNMCA) off the north coast of British Columbia, Canada. Ground-truth data for training and validation were collected using a towed underwater video camera. Prior to classification the WorldView-2 image (8 bands, 2m resolution) was processed following orthorectification, atmospheric correction, glint correction, land and optically deep water masking. An acoustic survey was conducted using a 200kHz echosounder and data were processed and interpolated using QTC IMPACT software. The WorldView-2 imagery performed best in mapping habitat in regions shallower than 3m, obtaining a total accuracy 75%, where it could identify the distribution of green algae (Ulva spp.), brown algae (Fucus spp.) and eelgrass (Zostera marina). The 200kHz data were unable to detect the distribution of brown and green algae but were able to map the distribution of eelgrass as well as a subtidal red algae (Chondrocanthus exasperatus) (total accuracy 80%). A final habitat map containing all habitat types present at the study site was produced using the output from both datasets. The study resulted in recommendations for remote mapping of submerged vegetation in temperate coastal area.

The role of summer monsoon-typhoons in the formation of nearshore coarse-grained ripples, depression, and sand-ridge systems along the Shimizu coast, Suruga Bay facing the Pacific Ocean, Japan

Coarse-grained ripples (CGRs) develop within the seafloor depression–sand ridge systems along the Shimizu coast, in the northwestern part of Suruga Bay facing the Pacific Ocean, central Japan. In this paper, we analyze data from high-resolution bathymetry, seafloor observation by an underwater video camera, and high-resolution seismic surveys and seafloor trenching of shallow strata, obtained between 2005 and 2007, to describe their geomorphological and sedimentological characteristics in detail, and to examine the formative processes and maintenance of the systems. In water depths of 5–30 m, CGRs occur in seafloor depressions that are approximately 40–70 cm deeper than the surrounding sandy seafloor. In many cases, the ripples develop in depressions between shore-normal sand ridges composed mainly of fine sand (< 70 cm high, 100–400 m long) on a relatively narrow shelf. The alongshore width of the sand ridges is 10–100 m, and that of the depressions is 10–150 m. The CGRs (wavelength < 3.5 m, height < 30 cm) have almost shore-parallel crests with a symmetrical or slightly asymmetrical shape, suggesting wave-generated oscillating flows. The crests of the lager ripples are composed of gravel (maximum long axis: 5–8 cm) and the troughs consist of fine to very fine sand. The CGR–depression–sand ridge systems develop widely during the passage of typhoons in the summer–autumn seasons. At the narrower shelf, the surface fine-grained sediments and the surface and subsurface coarse-grained sediments, which form the sand ridges and the CGRs respectively, are repeatedly eroded and redeposited during typhoon-related storms. In contrast, active sediments are currently limited to the surface fine deposits on the wider shelf areas. The sediments that make up the CGRs appear to be derived from both modern beach sediments and relict sediments. We postulate that the CGR–depression–sand ridge system appears to be controlled mainly by both seafloor erosion and offshore-directed sediment transport during storms, and these processes may depend on the shelf width. In fact, the sand ridges (covering the CGRs) that imply significant offshore-directed transport only develop on the narrower shelf. The distribution and seabed expression of the CGRs is constrained by the thickness and distribution of surface-covering sandy sediments, such as the sand ridges. This represents a new interpretation of the distribution of CGRs within seafloor depressions on the shelf of an active margin that receives a large supply of sandy and gravelly fluvial sediments, and differs from the processes seen on the sediment-starved shelves of passive margins. • We present seasonal morphological variations in nearshore coarse-grained ripples. • Ripples within the depression–sand ridge system only occur on the narrower shelf. • The system is significantly reorganized by typhoon-related storms. • Morphology of sand ridges covering the ripples reveals offshore transport to canyon. • Ripple distribution is constrained by the thickness of surface sandy deposits.

Evaluating the Effectiveness of the Pickering Nuclear Generating Station Fish Diversion System Barrier Net

AbstractBarrier nets can be an effective alternative for reducing impingement mortality of fish at power plant intakes. In 2010, a paired, split‐beam hydroacoustic method was used as the primary assessment tool for comparing relative fish density between the lake (“outside”) and station (“inside”) side of the Pickering Nuclear Generating Station fish diversion system (FDS) barrier net while it was in place. Behavioral information was also collected using a DIDSON acoustic camera and underwater video camera to determine fish responses to the FDS. Verification monitoring was completed using conventional gill netting. The DIDSON provided useful and valuable information on relative fish densities, relative school sizes, and behavior of fish as individuals, small groups, or schools on both the outside and inside of the FDS, as well as general behavior of fish approaching the FDS. There was no evidence of passage through the net based on DIDSON evaluation; however, fish passage occurred when the FDS net was considered to be in a degraded condition (from biofouling or storm events, or both) and passage occurred over the net, not through it. Analysis of the hydroacoustic data based on the weighted average biomass indicated that FDS effectiveness was 75, 98, and 100% for the spring, summer, and fall periods, respectively, and 98% for the three seasons combined. The summer and fall estimates were based on net performance under optimal net‐deployment conditions and if the net degrades, effectiveness is reduced significantly as observed in the spring data. Our study results were supported by impingement monitoring at the station whereby impingement biomass was reduced by greater than 80% for each of the first 3 years after installation compared with before installation of the barrier net. Overall, the FDS was demonstrated to offer significant fish protection from potential impingement at the Pickering Nuclear Generating Station.Received July 21, 2013; accepted December 6, 2013

人工集鱼装置对热带金枪鱼类摄食模式的影响研究进展

热带金枪鱼类具有聚集在漂浮物体周围的行为特性，形成的集群表现稳定，可捕性较高。以此特性，金枪鱼围网渔业研制并投放了大量的人工集鱼装置（Fish Aggregation Device，FAD）用于聚集并捕捞金枪鱼。然而，大规模出现的FAD会使某些海域海面漂浮物的密度迅速增加，从而在一定程度上人为地改变了金枪鱼的表层栖息环境，对金枪鱼种群具有一系列可能的潜在负面影响，摄食模式的改变就是其中之一。归纳并综合了近年来国内外关于FAD对金枪鱼类摄食模式影响的相关研究，从摄食行为、日摄食量、饵料种类与组成以及生态位宽度4个方面对比了随附于FAD的金枪鱼和自由状态下同类的不同，发现大多情况下FAD的存在会使金枪鱼的摄食模式发生一定的改变。最后，归纳了过往实验存在的不足，对今后研究的发展方向进行了展望。;Tropical tunas are a kind of highly migratory oceanic fishes whose food organisms in perched waters are relatively scarce and are distributed as patches. The tunas are obliged to swim quickly in response to dynamic changes of its prey because of hardly lasting aggregation of food organisms. Tropical tunas are inclined to form natural aggregations which are usually referred to as free swimming schools. In early days, however, the artisanal fisherman noted that the tropical tunas have the habit of gathering around natural floating objects such as logs, seaweed mats, branches and palm leaves, forming stable aggregations, termed as floating-objects-associated schools. They found that fishing was much efficient near these objects than in an open ocean. Tuna purse seine fisheries utilized this type of behavior to develop a great number of fish aggregation devices (FADs) for aggregating tuna and thus improve harvest efficiency. Two types of FADs are often used: drifting FADs (dFADs) and anchored FADs (aFADs). Since the first FAD deployments, FADs-based fishing technology had developed rapidly throughout the early 1990s, and FADs have been generally accepted as an effective mean to increase catch rates and reduce the energy consumption of purse seiners. The large-scale use of FADs, however, considerably increases the density of floating objects in some waters, and in turn, to some extent, artificially changes the surface habitat of the tuna. This may impose a series of potentially negative effects on tuna populations, such as changes in patterns of aggregation, feeding pattern and migratory movement and the decline of physical conditions for the population. Of those mentioned-above side effects, changes in the feeding pattern may have more profound impacts on fish populations as it exerts a direct effect on key life history processes, such as growth and reproduction. In the past 30 years, many studies have been conducted to evaluate whether and how FADs affect the feeding pattern. However, the results from these studies are still inconclusive and contradictory.<br> This review summarizes recent studies in regard to the tuna feeding patterns as influenced by FADs. We compare differences of feeding behavior, daily rations, the types of prey and ecological niche width between FAD-associated and free swimming tuna schools. It implies that, FADs tend to alter the large-scale migratory movements to some extents, but not the local and small-scale migratory movements. FADs may also influence the stomach contains and the rates of empty stomach. Thus, FADs, in most cases, do in fact change feeding pattern and behavior. This review also identifies shortcomings in previous studies in their research methods and contents, and accordingly proposes new research approaches, such as the use of underwater video camera to observe the feeding behavior of tunas directly, take advantage of remaining stomach contents to rebuild diet composition for the estimation of the daily rations. Stable isotope analysis (SIA) can also help improve our understanding of trophic ecology for tunas. We also include a discussion on possible future research direction in evaluating impacts of FADs on feeding behavior for tunas.

Importance of sagittal kick symmetry for underwater dolphin kick performance

The purpose of this study was to determine how sagittal kick symmetry in the underwater dolphin kick (UDK) between the downkick and upkick phases is related to UDK performance. Fifteen adult male competitive swimmers ranging from provincial to international level were filmed performing three trials each of maximum effort UDK over 15m using an underwater video camera. Video frames were manually digitized and each subjects’ single fastest trial was evaluated for between-subject comparisons. Kinematic variables were calculated for each individual and Pearson product-moment correlations between the average horizontal centre of mass velocity (Vx) and all kinematic variables were calculated. Horizontal velocity during the downkick, horizontal velocity during the upkick, relative time spent in each phase, maximum chest flexion angle, maximum knee and ankle extension angles, the ratio of flexion/extension for chest, knee and ankle angles, and maximum vertical toe velocity during the upkick phase correlated significantly with Vx (p<0.05). The ratio of downkick vertical toe velocity/upkick vertical toe velocity was significantly negatively correlated with Vx (p<0.05). These results indicate the importance of kick symmetry for UDK performance, and indicate that performing the upkick phase well appears to be most important for UDK performance.

Estimates of acoustic target strength for giant jellyfish Nemopilema nomurai Kishinouye in the coastal Northwest Pacific

Abstract Acoustic target strength (TS) measurements were made of ex situ giant jellyfish Nemopilema nomurai Kishinouye at 38 and 120 kHz. These TS data may be useful for developing acoustic scattering models, and surveying giant jellyfish distributions and biomasses. Each jellyfish was tethered in seawater using a monofilament line that vertically penetrated its bell's centre. During the acoustic measurements, an underwater video camera was used to continuously monitor the jellyfish's behaviour. Acoustic measurements were made using split-beam transducers. TS measurements were made of 27 individual jellyfish, but data were analysed for 23 specimens (bell diameter in air, Dair = 21–65 cm) at 38 kHz, and 19 specimens (Dair = 21–46 cm) at 120 kHz, respectively. Least-squares regression fits of TS vs. log(Dair) were TS38kHz = 20•log10Dair–82.7 (r = 0.76) and TS120kHz = 20•log10Dair–86.7 (r = 0.79). The mean TS values at 38 and 120 kHz, using the average Dair = 40.3 cm and 35.5 cm, respectively, were −50.6 and −55.7 dB. The reduced TS, a function of the ratio of Dair to wavelength (λ), was RTS(Dair/λ) = −6.1•log10(Dair/λ) –36.1 (r = 0.51). These RTS values decreased with increasing Dair/λ. Symbiotic medusa shrimp (Latreutes anoplonyx Kemp) contributed negligible bias to our TS measurements of giant jellyfish. These ex situ TS measurements may be used in acoustic surveys to estimate the distributions and biomasses of N. nomurai.

Thresher Sharks Use Tail-Slaps as a Hunting Strategy

The hunting strategies of pelagic thresher sharks (Alopias pelagicus) were investigated at Pescador Island in the Philippines. It has long been suspected that thresher sharks hunt with their scythe-like tails but the kinematics associated with the behaviour in the wild are poorly understood. From 61 observations recorded by handheld underwater video camera between June and October 2010, 25 thresher shark shunting events were analysed. Thresher sharks employed tail-slaps to debilitate sardines at all times of day. Hunting events comprised preparation, strike, wind-down recovery and prey item collection phases, which occurred sequentially. Preparation phases were significantly longer than the others, presumably to enable a shark to windup a tail-slap. Tail-slaps were initiated by an adduction of the pectoral fins, a manoeuvre that changed a thresher shark's pitch promoting its posterior region to lift rapidly, and stall its approach. Tail-slaps occurred with such force that they may have caused dissolved gas to diffuse out of the water column forming bubbles. Thresher sharks were able to consume more than one sardine at a time, suggesting that tail-slapping is an effective foraging strategy for hunting schooling prey. Pelagic thresher sharks appear to pursue sardines opportunistically by day and night, which may make them vulnerable to fisheries. Alopiids possess specialist pectoral and caudal fins that are likely to have evolved, at least in part, for tail-slapping. The evidence is now clear; thresher sharks really do hunt with their tails.

SmeltCam: Underwater Video Codend for Trawled Nets with an Application to the Distribution of the Imperiled Delta Smelt

Studying rare and sensitive species is a challenge in conservation biology. The problem is exemplified by the case of the imperiled delta smelt Hypomesus transpacificus, a small delicate fish species endemic to the San Francisco Estuary, California. Persistent record-low levels of abundance and relatively high sensitivity to handling stress pose considerable challenges to studying delta smelt in the wild. To attempt to overcome these and other challenges we have developed the SmeltCam, an underwater video camera codend for trawled nets. The SmeltCam functions as an open-ended codend that automatically collects information on the number and species of fishes that pass freely through a trawled net without handling. We applied the SmeltCam to study the fine-scale distribution of juvenile delta smelt in the water column in the upper San Francisco Estuary. We learned that during flood tides delta smelt were relatively abundant throughout the water column and that during ebb tides delta smelt were significantly less abundant and occurred only in the lower half and sides of the water column. The results suggest that delta smelt manipulate their position in the water column to facilitate retention in favorable habitats. With the application of the SmeltCam we increased the survival of individual delta smelt by 72% compared to using a traditional codend, where all of the fish would have likely died due to handling stress. The SmeltCam improves upon similar previously developed silhouette photography or video recording devices and demonstrates how new technology can be developed to address important questions in conservation biology as well as lessen the negative effects associated with traditional sampling methods on imperiled species.

Identity and behaviour of herbivorous fish influence large-scale spatial patterns of macroalgal herbivory in a coral reef

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 482:227-240 (2013) - DOI: https://doi.org/10.3354/meps10262 Identity and behaviour of herbivorous fish influence large-scale spatial patterns of macroalgal herbivory in a coral reef Peter J. Michael1, Glenn A. Hyndes1, Mathew A. Vanderklift1,2, Adriana Vergés1,3,4,* 1Centre for Marine Ecosystems Research, School of Natural Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, Western Australia 6027, Australia 2CSIRO Wealth from Oceans Flagship, Private Bag 5, Wembley, Western Australia 6913, Australia 3Centre for Marine Bio-Innovation and Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2056, Australia 4Sydney Institute of Marine Science, Building 19, Chowder Bay Rd, Mosman, New South Wales 2088, Australia *Corresponding author. Email: a.verges@unsw.edu.au ABSTRACT: The functional role of macroalgae-consuming fishes is particularly important in coral reefs, as they can mediate the recovery of degraded systems when macroalgae become established. However, herbivory on coral reefs is often spatially and temporally variable, and the mechanisms that underpin variation in the consumption of algae are largely unknown. In this study, we examined local (within-reef, 100s of m) and broad-scale (regional, 100s of km) patterns of macroalgal herbivory along the spatial extent of Ningaloo Reef in northwestern Australia. Using underwater video cameras, we quantified the feeding rates of individual fish on a dominant macroalga Sargassum myriocystum, and we quantified social feeding behaviour to determine whether patterns in algal removal are influenced by whether fish feed as solitary individuals or as part of single-species or multi-species groups. While 23 fish species were observed biting macroalgae, spatial patterns in the intensity of herbivory were strongly driven by 3 species: Naso unicornis, Kyphosus vaigiensis and K. bigibbus. Feeding rates by individuals of these 3 species were always highest when individuals were part of monospecific groups, and we found a strong positive relationship between spatial patterns in the amount of macroalgae removed and the proportion of bites taken as part of groups, irrespective of fish size. This study highlights the importance of species-specific algae–herbivore interactions in coral reefs and shows that local variation in feeding behaviour is an important trait that contributes to explain spatial variability in macroalgal herbivory. KEY WORDS: Herbivory · Macroalgae · Group feeding · Naso unicornis · Kyphosus vaigiensis · Kyphosus bigibbus · Ningaloo Reef Full text in pdf format PreviousNextCite this article as: Michael PJ, Hyndes GA, Vanderklift MA, Vergés A (2013) Identity and behaviour of herbivorous fish influence large-scale spatial patterns of macroalgal herbivory in a coral reef. Mar Ecol Prog Ser 482:227-240. https://doi.org/10.3354/meps10262 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 482. Online publication date: May 22, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Automatic front-crawl temporal phase detection using adaptive filtering of inertial signals

This study introduces a novel approach for automatic temporal phase detection and inter-arm coordination estimation in front-crawl swimming using inertial measurement units (IMUs). We examined the validity of our method by comparison against a video-based system. Three waterproofed IMUs (composed of 3D accelerometer, 3D gyroscope) were placed on both forearms and the sacrum of the swimmer. We used two underwater video cameras in side and frontal views as our reference system. Two independent operators performed the video analysis. To test our methodology, seven well-trained swimmers performed three 300 m trials in a 50 m indoor pool. Each trial was in a different coordination mode quantified by the index of coordination. We detected different phases of the arm stroke by employing orientation estimation techniques and a new adaptive change detection algorithm on inertial signals. The difference of 0.2 ± 3.9% between our estimation and video-based system in assessment of the index of coordination was comparable to experienced operators’ difference (1.1 ± 3.6%). The 95% limits of agreement of the difference between the two systems in estimation of the temporal phases were always less than 7.9% of the cycle duration. The inertial system offers an automatic easy-to-use system with timely feedback for the study of swimming.

Predation of hatchery-cultured juvenile red king crabs (Paralithodes camtschaticus) in the wild

The ecologically and commercially important red king crab (Paralithodes camtschaticus) is depleted throughout much of the North Pacific and thought to be recruitment-limited, making it an appropriate candidate for stock enhancement efforts. Information on predation of newly settled red king crabs in nearshore habitats is needed to assess the feasibility of large-scale releases. We tethered hatchery-cultured red king crabs of two sizes (range: 1.75–4.08 mm carapace width) in the field for 24 h trials in July and September 2011 and used underwater video cameras to identify predators and predation susceptibility. We identified hermit crabs (Pagurus spp.), Alaskan ronquil (Bathymaster caeruleofasciatus), Arctic shanny (Sticheus punctatus), northern rock sole (Lepidopsetta polyxystra), and kelp greenling (Hexagrammos decagrammus) as predators. Survival did not vary by body size or deployment month; however, small crabs were consumed sooner than large crabs. Most predation events occurred in daylight hours, with the exception of Alaskan ronquil. Our results suggest stock enhancement efforts should consider predator assemblages when developing release strategies. Future studies should investigate spatial variation in predation pressure at multiple locations on broad temporal scales to optimize release strategies and understand population-level effects.

Comparison of trap and underwater video gears for indexing reef fish presence and abundance in the southeast United States

It is challenging to manage reef fish species in the Southeast U.S. Continental Shelf Large Marine Ecosystem (SUSLME) due to life history strategies that make them vulnerable to overexploitation, difficulty of sampling reef fish in high-relief hard bottom habitats, and fluctuations in utility of fishery-dependent data. In response to declines in fishery-dependent data due to fishery closures, fishery-independent sampling of reef fish has become even more critical to stock assessment. Here we test whether a long-term chevron trapping survey could benefit from the addition of underwater video cameras. Sampling occurred on continental shelf and shelf break habitats (15–83m deep) between northern Georgia and central Florida. Reef fish frequency of occurrence was significantly higher on video compared to traps for 11 of 15 species analyzed, and the increase ranged from 38% to infinity for these 11 species. Frequency of occurrence for the four remaining species was not significantly different between traps and video. Although positive relationships were observed between log-transformed trap and video indices of abundance for five selected reef fish species, considerable amounts of unexplained variation existed and the relationship for three species was nonlinear. Underwater video can be a beneficial addition to a long-term trapping survey by increasing the frequency of occurrence for most reef fish species, which should translate into improved indices of reef fish abundance in the SUSLME.