An enhanced underwater camera apparatus for seabed observation of megabenthic epifauna in the northern Yellow Sea

Seabed photographing has been applied with various underwater camera apparatuses(UCAs)for observations of megabenthic epifauna,which reveals more details than traditional sampling tools do.In this study,we improved a UCA named a towed underwater video-camera system(TUV system)with image processing software for seabed photographing in coastal areas up to 100 m.In May 2017,the TUV system was tested at 4 stations in the Zhangzi Island marine area in the northern Yellow Sea to investigate local megabenthic epifauna,especially brittle stars.At each station,more than 500 good seabed photographs each in area of 0.1550 m2 were obtained in just 10 min.Almost all of the epifauna larger than 1 mm could be identified from the photographs,including echinoderms,bivalves,cnidarians,and crustaceans.Three dominant brittle stars(Ophiopholis mirabilis,Ophiura sarsii vadicola,and Stegophiura sladeni)were spotted,and their abundance,disc diameter,cluster size,and coverage area were calculated and analyzed from the seabed photographs.The results show that the TUV system could be applied in coastal waters of hard sandy bottoms and could be used for quantitative investigations of megabenthic epifauna.

Underwater Image Enhancement Based on the Dark Channel Prior and Attenuation Compensation

Aimed at the two problems of underwater imaging, fog effect and color cast, an Improved Segmentation Dark Channel Prior(ISDCP) defogging method is proposed to solve the fog effects caused by physical properties of water. Due to mass refraction of light in the process of underwater imaging, fog effects would lead to image blurring. And color cast is closely related to different degree of attenuation while light with different wavelengths is traveling in water. The proposed method here integrates the ISDCP and quantitative histogram stretching techniques into the image enhancement procedure. Firstly, the threshold value is set during the refinement process of the transmission maps to identify the original mismatching, and to conduct the differentiated defogging process further. Secondly, a method of judging the propagating distance of light is adopted to get the attenuation degree of energy during the propagation underwater. Finally, the image histogram is stretched quantitatively in Red-Green-Blue channel respectively according to the degree of attenuation in each color channel. The proposed method ISDCP can reduce the computational complexity and improve the efficiency in terms of defogging effect to meet the real-time requirements. Qualitative and quantitative comparison for several different underwater scenes reveals that the proposed method can significantly improve the visibility compared with previous methods.

Underwater video cameras allow for detection of North American giant salamanders (Cryptobranchus alleganiensis alleganiensis) in both captive and wild streams

Captive propagation and translocation are becoming vital components of conservation and management strategies for Eastern hellbender(Cryptobranchus a.alleganiensis)populations.Zoos,aquaria,universities,and state and federal agencies are concomitantly collaborating on the protection,education,and maintenance of captive populations of this unusual,cryptic salamander.Conservation strategies include the use of artificial nesting structures,collection of eggs from the wild,and head-starting individuals in zoos or hatcheries.The effects of these strategies need to be monitored,however,traditional survey and monitoring methods for the species in the wild involves rock-lifting,which has the potential to both harm habitat and alter reproductive behavior.Therefore,there is a need to develop effective,non-invasive and non-destructive methods of monitoring both wild and captive populations of Eastern hellbenders.Herein,we compare two simple,affordable,underwater video and camera systems(borescope and Aqua-Vu cameras)in their ability to 1)facilitate detection of adults under potential cover items and 2)facilitate nest detection and monitoring in both wild and captive environments.Both cameras were successful in detecting individual hellbender presence,albeit with different resolutions and detection times.The borescope was better at accessing deep cavities given its large flexible attachment which allowed for greater flexibility of scanning crevices of adult shelters.However,search time increased and even low levels of suspended sediment reduced visibility with the borescope.The Aqua-Vu camera provided greater overall visibility and faster detection of individuals under both natural and artificial shelters.There was a significant difference in the amount of time required to detect hellbenders with each camera design when searching under natural rocks(borescope:median=67.8 s,Aqua-Vu:median=39.1 s;Kruskal Wallis Test H=15.62,p<0.001)and artificial shelters(borescope:median=30.9 s,Aqua-Vu:median=13 s;Kruskal Wallis Test H=25.23,p<0.0001).We detected 8 natural nests with actively guarding males and only one individual using a wild artificial shelter.We recommend hellbender researchers utilize a combination of underwater video cameras to suit their specific survey goals in both captive and field settings.Moreover,we recommend zoo staff incorporate these methods to not only monitor captive populations but also to potentially record breeding behavior in zoos and aquariums.