Behaviour Of Marine Predators Research Articles

An Efficient Marine Predators Algorithm for Solving Multi-Objective Optimization Problems: Analysis and Validations

Recently, a new strong optimization algorithm called marine predators algorithm (MPA) has been proposed for tackling the single-objective optimization problems and could dramatically fulfill good outcomes in comparison to the other compared algorithms. Those dramatic outcomes, in addition to our recently-proposed strategies for helping meta-heuristic algorithms in fulfilling better outcomes for the multi-objective optimization problems, motivate us to make a comprehensive study to see the performance of MPA alone and with those strategies for those optimization problems. Specifically, This paper proposes four variants of the marine predators' algorithm (MPA) for solving multi-objective optimization problems. The first version, called the multi-objective marine predators' algorithm (MMPA) is based on the behavior of marine predators in finding their prey. In the second version, a novel strategy called dominance strategy-based exploration-exploitation (DSEE) recently-proposed is effectively incorporated with MMPA to relate the exploration and exploitation phase of MPA to the dominance of the solutions-this version is called M-MMPA. DSEE counts the number of dominated solutions for each solution-the solutions with high dominance undergo an exploitation phase; the others with small dominance undergo the exploration phase. The third version integrates M-MMPA with a novel strategy called Gaussian-based mutation, which uses the Gaussian distribution-based exploration and exploitation strategy to search for the optimal solution. The fourth version uses the Nelder-Mead simplex method with M-MMPA (M-MMPA-NMM) at the start of the optimization process to construct a front of the non-dominated solutions that will help M-MMPA to find more good solutions. The effectiveness of the four versions is validated on a large set of theoretical and practical problems. For all the cases, the proposed algorithm and its variants are shown to be superior to a number of well-known multi-objective optimization algorithms.

Development of an animal-borne “sonar tag” for quantifying prey availability: test deployments on northern elephant seals

Developments in electronic tagging technologies have provided unprecedented insight into the movements and behavior of marine predators. Concurrent information on the prey of these tracked animals, however, is mostly lacking. We developed and tested a prototype autonomous echosounder (aka the sonar tag) for deployment on large marine animals intended to provide quantification of their prey fields. The resulting fully autonomous, internally recording prototype sonar tag operated at a power of 1 W and a frequency of 200 kHz. A series of test deployments were successfully conducted on four juvenile female elephant seals (Mirounga angustirostris) captured at the Ano Nuevo State Reserve, California, and released short distances away. Translocated seals were instrumented with a sonar tag and a Fastloc GPS tag with an integrated time-depth recorder (TDR). All four animals returned to land after 3–18 days, making dives to depths of up to 778 m. Strong backscattering from the bottom was observed during many dives, indicating an often close association with the seafloor. Numerous observations of strongly scattering targets, potentially indicative of prey, were also made in the water column, often associated with particular dive and movement behaviors. During dives identified as foraging-type and also travel-type, one animal with the acoustic transducer on its head showed successive targets getting increasingly closer to the animal, possibly consistent with prey pursuit. These results demonstrate the value of active acoustic backscattering measurements made from free-ranging animals, complementing the ecological insight afforded by traditional depth- and position-logging tags. Future refinements will include further miniaturization, performance optimization, and extensions in the deployment duration.

Do man‐made structures and water depth affect the diel rhythms in click recordings of harbor porpoises (Phocoena phocoena)?

AbstractThe construction of industrial offshore structures may lead to colonization by a variety of marine organisms resulting in locally enhanced biodiversity and biomass, which may then affect the habitat use and behavior of marine predators. For harbor porpoises high nocturnal echolocation activity was demonstrated near industrial structures and it was hypothesized that this was caused by increased feeding opportunities at night. Here we tested the hypothesis that bridge pillars will lead to more nocturnal echolocation activity by porpoises near them than at positions further away. The daily rhythms in porpoise detections near bridge pillars tended to be slightly more pronounced and a greater proportion of clicks occurred during the night. However, water depth had a greater impact on these rhythms, with more nocturnal porpoise echolocation activity and more pronounced daily rhythms in deeper waters. This may be related to different feeding techniques and prey choice by porpoises in deep and shallow water. In deeper water porpoises may be feeding pelagically on herring and cod, which show more activity and are easier to catch at night. In shallow water they may be targeting mainly gobies using a bottom feeding technique and this may not be more efficient at night.