Reduction of Species Identification Errors in Surveys of Marine Wildlife Abundance Utilising Unoccupied Aerial Vehicles (UAVs)

The advent of unoccupied aerial vehicles (UAVs) has enhanced our capacity to survey wildlife abundance, yet new protocols are still required for collecting, processing, and analysing image-type observations. This paper presents a methodological approach to produce informative priors on species misidentification probabilities based on independent experiments. We performed focal follows of known dolphin species and distributed our imagery amongst 13 trained observers. Then, we investigated the effects of reviewer-related variables and image attributes on the accuracy of species identification and level of certainty in observations. In addition, we assessed the number of reviewers required to produce reliable identification using an agreement-based framework compared with the majority rule approach. Among-reviewer variation was an important predictor of identification accuracy, regardless of previous experience. Image resolution and sea state exhibited the most pronounced effects on the proportion of correct identifications and the reviewers’ mean level of confidence. Agreement-based identification resulted in substantial data losses but retained a broader range of image resolutions and sea states than the majority rule approach and produced considerably higher accuracy. Our findings suggest a strong dependency on reviewer-related variables and image attributes, which, unless considered, may compromise identification accuracy and produce unreliable estimators of abundance

Izrael: Rekonstruirane procjene ukupnog izlova u Sredozemnom moru, 1950.–2010.

Over the past six decades, the Food and Agriculture Organization (FAO) has reported fisheries ‘landings’, not ‘total removals’ for Israel. Thus, public data do not include all removals, including discards, the recreational fishery, subsistence portions of the catch or Bluefin tuna catches. Moreover, FAO data inadvertently included landings by Gaza fishers in the Gaza Strip during the 1960s and 1970s. We reconstructed total removals for Israel fishing in the Mediterranean Sea using various anchor points from recent studies to account for the missing removals. We estimated total removals at slightly over 255,400 tonnes for 1950-2010, which are nearly 30% higher than the 198,136 t of Israel’s reported catch to FAO (after exclusion of data from the Gaza Strip). The major components of unreported removals were discards (over 37,400 t), dominated by the trawl fishery, and recreational removals (over 15,500 t), which account for a large and rapidly growing fishery sector in Israel. In contrast, subsistence catches (just under 4,000 t) are low, which is not unexpected for a developed country. Non-indigenous Indo-Pacific organisms are a large and growing component in the multispecies catch of Mediterranean fishers; however they appear to change species composition and mode of exploitation more than they affect the level of total removals. In the highly oligotrophic, yet fast changing Levantine Sea, the high discarding rates, use of unsustainable fishing methods and under-regulated fisheries (particularly the recreational sector) pose a threat to the integrity of the marine environment and the ecosystem services we expect from it.Tijekom proteklih šest desetljeća, FAO je davao izvješća o ulovu (iskrcajnom ulovu), ali ne i o ukupnom izlovu za Izrael. Stoga, javni podaci ne uključuju sve izlove, uključujući odbačeni ulov, ulov u rekreacijskom ribolovu, ulove u dopunskom ribolovu kao i ulove plavoperajne tune. Štoviše, FAO podaci nehotice uključuju i ulov ribara u pojasu Gaze tijekom 1960-ih i 1970- ih. Rekonstruirani su ukupni izlovi za Izraelski ribolov u Sredozemnom moru, koristeći razna polazišta iz nedavnih studija kako bi se obračunali nedostajući podaci o sveukupnom izlovu. Procijenjen ukupni izlov iznosi nešto više od 255.400 tona za razdoblje od 1950.-2010., koji je gotovo 30% veći od 198.136 t izraelskog prijavljenog ulova prema FAO (nakon odbacivanja podataka iz pojasa Gaze). Glavne komponente neprijavljenih izlova su: odbačeni ulov (preko 37.400 t), u kojem dominira koćarski ribolov, i rekreacijski izlov (preko 15.500 t), koji čini veliki i brzo rastući sektor ribarstva u Izraelu. Nasuprot tome, ulovi u dopunskom ribolovu (nešto manje od 4.000 t) su niski, što i nije neočekivano za razvijene zemlje. Strani organizmi iz Crvenog mora su velika i rastuća komponenta u ulovima mediteranskih ribara, no čini se da će isti promijeniti sastav vrsta kao i način iskorištavanja živih bogatstava znatno više nego što recimo utječu na razini ukupnog izlova. U vrlo oligotrofnom, ali i brzo mijenjajućem Levantskom moru, velike količine odbačenog ulova, postojeća uporaba neodrživih metoda ribolova kao i slabo reguliran ribolov (osobito unutar rekreativnog sektora) predstavljaju prijetnju integritetu morskog ekosustava te ujedno time i onome što možemo očekivati od njega

Drivers of population structure of the bottlenose dolphin (Tursiops truncatus) in the Eastern Mediterranean Sea

The drivers of population differentiation in oceanic high dispersal organisms, have been crucial for research in evolutionary biology. Adaptation to different environments is commonly invoked as a driver of differentiation in the oceans, in alternative to geographic isolation. In this study, we investigate the population structure and phylogeography of the bottlenose dolphin (Tursiops truncatus) in the Mediterranean Sea, using microsatellite loci and the entire mtDNA control region. By further comparing the Mediterranean populations with the well described Atlantic populations, we addressed the following hypotheses: (1) bottlenose dolphins show population structure within the environmentally complex Eastern Mediterranean Sea; (2) population structure was gained locally or otherwise results from chance distribution of preexisting genetic structure; (3) strong demographic variations within the Mediterranean basin have affected genetic variation sufficiently to bias detected patterns of population structure. Our results suggest that bottlenose dolphin exhibits population structures that correspond well to the main Mediterranean oceanographic basins. Furthermore, we found evidence for fine scale population division within the Adriatic and the Levantine seas. We further describe for the first time, a distinction between populations inhabiting pelagic and coastal regions within the Mediterranean. Phylogeographic analysis suggests that current genetic structure, results mostly from stochastic distribution of Atlantic genetic variation, during a recent postglacial expansion. Comparison with Atlantic mtDNA haplotypes, further suggest the existence of a metapopulation across North Atlantic/Mediterranean, with pelagic regions acting as source for coastal environments

Depth Partitioning and Diel Movement of Two Large Carcharhinid Sharks in Extremely Shallow Waters

Two species of carcharhinid sharks aggregate every winter at the warm water effluent of a coastal power plant on the Israeli Mediterranean coast. The two species (Carcharhinus obscurus and Carcharhinus plumbeus) cooccur in a highly confined area for several months every year and are highly associated with the area in and around the hot water effluent. Niche partitioning has recently been suggested as a mechanism that enables the coexistence of similar shark species by resource partitioning, spatial partitioning, and temporal partitioning. In this study, we used acoustic telemetry to study the individual diel movement and activity patterns within this enclosed area and examined the differences between the two species sharing it. Although this location only reaches a maximum depth of 7.5 m, we found both species perform a diel vertical movement, rising closer to the surface at night and moving deeper during daytime. Furthermore, the two shark species swam at different depths both day and night, with C. obscurus swimming in the upper column, about 2 m shallower than C. plumbeus. The very small scale of movement, which nearly equals the sharks’ body length, suggests movement patterns might be conserved at the species level. Moreover, spatiotemporal differences between the two species may reflect a mean of interspecific partitioning that occurs even in a highly confined and shallow habitat

Depth Partitioning and Diel Movement of Two Large Carcharhinid Sharks in Extremely Shallow Waters

Two species of carcharhinid sharks aggregate every winter at the warm water effluent of a coastal power plant on the Israeli Mediterranean coast. The two species (Carcharhinus obscurus and Carcharhinus plumbeus) cooccur in a highly confined area for several months every year and are highly associated with the area in and around the hot water effluent. Niche partitioning has recently been suggested as a mechanism that enables the coexistence of similar shark species by resource partitioning, spatial partitioning, and temporal partitioning. In this study, we used acoustic telemetry to study the individual diel movement and activity patterns within this enclosed area and examined the differences between the two species sharing it. Although this location only reaches a maximum depth of 7.5 m, we found both species perform a diel vertical movement, rising closer to the surface at night and moving deeper during daytime. Furthermore, the two shark species swam at different depths both day and night, with C. obscurus swimming in the upper column, about 2 m shallower than C. plumbeus. The very small scale of movement, which nearly equals the sharks’ body length, suggests movement patterns might be conserved at the species level. Moreover, spatiotemporal differences between the two species may reflect a mean of interspecific partitioning that occurs even in a highly confined and shallow habitat

A Systematic Review of the Behavioural Changes and Physiological Adjustments of Elasmobranchs and Teleost’s to Ocean Acidification with a Focus on Sharks

In recent years, much attention has been focused on the impact of climate change, particularly via ocean acidification (OA), on marine organisms. Studying the impact of OA on long-living organisms, such as sharks, is especially challenging. When the ocean waters absorb anthropogenic carbon dioxide (CO2), slow-growing shark species with long generation times may be subjected to stress, leading to a decrease in functionality. Our goal was to examine the behavioral and physiological responses of sharks to OA and the possible impacts on their fitness and resilience. We conducted a systematic review in line with PRISMA-Analyses, of previously reported scientific experiments. We found that most studies used CO2 partial pressures (pCO2) that reflect representative concentration pathways for the year 2100 (e.g., pH ~7.8, pCO2 ~1000 μatm). Since there is a considerable knowledge gap on the effect of OA on sharks, we utilized existing data on bony fish to synthesize the available knowledge. Given the similarities between the behaviors and physiology of these two superclasses’ to changes in CO2 and pH levels, there is merit in including the available information on bony fish as well. Several studies indicated a decrease in shark fitness in relation to increased OA and CO2 levels. However, the decrease was species-specific and influenced by the intensity of the change in atmospheric CO2 concentration and other anthropogenic and environmental factors (e.g., fishing, temperature). Most studies involved only limited exposure to future environmental conditions and were conducted on benthic shark species studied in the laboratory rather than on apex predator species. While knowledge gaps exist, and more research is required, we conclude that anthropogenic factors are likely contributing to shark species’ vulnerability worldwide. However, the impact of OA on the long-term stability of shark populations is not unequivocal

Classification of Underwater Fish Images and Videos via Very Small Convolutional Neural Networks

The automatic classification of fish species appearing in images and videos from underwater cameras is a challenging task, albeit one with a large potential impact in environment conservation, marine fauna health assessment, and fishing policy. Deep neural network models, such as convolutional neural networks, are a popular solution to image recognition problems. However, such models typically require very large datasets to train millions of model parameters. Because underwater fish image and video datasets are scarce, non-uniform, and often extremely unbalanced, deep neural networks may be inadequately trained, and undergo a much larger risk of overfitting. In this paper, we propose small convolutional neural networks as a practical engineering solution that helps tackle fish image classification. The concept of “small” refers to the number of parameters of the resulting models: smaller models are lighter to run on low-power devices, and drain fewer resources per execution. This is especially relevant for fish recognition systems that run unattended on offshore platforms, often on embedded hardware. Here, established deep neural network models would require too many computational resources. We show that even networks with little more than 12,000 parameters provide an acceptable working degree of accuracy in the classification task (almost 42% for six fish species), even when trained on small and unbalanced datasets. If the fish images come from videos, we augment the data via a low-complexity object tracking algorithm, increasing the accuracy to almost 49% for six fish species. We tested the networks with images obtained from the deployments of an experimental system in the Mediterranean sea, showing a good level of accuracy given the low quality of the dataset

Correction: Regev, Y., et al. Molecular Identification and Characterization of Vibrio Species and Mycobacterium Species in Wild and Cultured Marine Fish from the Eastern Mediterranean Sea. Microorganisms 2020, 8, 863

We would like to change the authors’ affiliation of paper [...

Two Decades of Coastal Dolphin Population Surveys in Israel, Eastern Mediterranean

Along the Mediterranean coast of Israel, two near-shore dolphin species are prevalent; Tursiops truncatus (least concern, IUCN) and Delphinus delphis (endangered, IUCN). Ship-board surveys and sporadic sightings over the last two decades have shown that the two differ in distribution—T. truncatus is found along the entire coast and D. delphis only in the south. The environmental and anthropological factors affecting these species’ spatial distribution and determining their habitat preferences in this area are largely unknown. This work is a first attempt at summarizing 20 years of observations and studying habitat preferences for both species, by use of Generalized Additive Models. T. truncatus was found to be present in all areas of the continental shelf where survey effort coverage was sufficient, with a high affinity towards bottom trawlers. Model results showed D. delphis distribution to be associated to (shallow) water depths, though the factors driving their limited latitudinal distribution currently remain unknown. It is evident that T. truncatus and D. delphis are present in segregated areas of the Israeli continental shelf and T. truncatus currently sustains a delicate balance with continuously shifting human activities, while the drivers of D. delphis distribution are more specified, yet still not fully understood