Hunting a dynamic target that exhibits random and unexpected behavior in an unknown environment poses significant challenges. In this research paper, we propose a novel method for efficiently localizing and hunting such targets by leveraging collaborative work among a team of hunters. The target provides one type of signal that lacks precise target location data, resembling an unstable GPS, and the hunters are not sophisticated robots, which means they can only exploit this information. The hunting process is divided into four stages: exploration, summoning, encircling, and hunting. During the exploration stage, the hunters actively search for the target. Once a hunter detects the target, the summoning stage is initiated, alerting the other hunters to converge on the target’s location. As more than one robot detects the target, the encircling stage begins, aiming to surround the target for effective capture. Finally, during the hunting stage, multiple robots work together to capture the target. The efficiency and effectiveness of this method are validated through numerical simulations using MATLAB and the ROS-Gazebo simulator. The results demonstrate the promising potential of this method for successfully localizing and hunting dynamic targets in unknown environments.

Recently, path planning of multi-autonomous mobile robot systems is one of the interesting topics in scientific research due to its complexity and its wide use in many fields, such as modern industry, war field, and logistics. Q-learning algorithm which is a sort of reinforcement learning is a widely used method in autonomous mobile robot path planning, thanks to its capacity of learning by itself in any environment without the need for prior knowledge. To increase the convergence speed of the Q-learning algorithm and adapt it to robotics and multi-robot systems, the Multi-Robot Improved Q-Learning algorithm (MRIQL) is proposed. The Artificial Potential Field algorithm (APF) is used to initialize the Q-learning. During learning, a restricting mechanism is used to prevent unnecessary actions while exploring. This Improved Q-learning algorithm is adapted to multi-robot system path planning by controlling and adjusting the policies of the robots to generate an optimal and collision-free path for each robot. We introduce a simulation environment for mobile robots based on Robot Operating System (ROS) and Gazebo. The experimental results and the simulation demonstrate the validity and the efficiency of the proposed algorithm.

Growth parameters and mortality rates were determined from a sample of 115 individuals of Xyrich-tys novacula collected with handlines in the same sector of the Gulf of Tunis between June 2015 and October 2019. The sample size range was between 9.8 and 19.2 cm total length (TL) with mean TL of females being significantly smaller than that of males. The estimated length-weight relationships were TW0.002 TL3.383 for males and TW0.003 TL3.320 for females, and both showed positive allometric somatic growth. Age was evaluated from whole sagittal otoliths and 6 age classes were determined. Von Bertalanffy growth parameters for the whole sample were: TL & INFIN; = 17.18 cm, K = 1.079 year-1, t0 = 0. Calculated growth performance index was 0 = 2.50 cm year-1. Total mortality (Z) was 1.3 year-1, natural mortality (M) was 0.949 year-1, fishing mortality (F) was 0.35 year-1, and exploitation rate (E) was 0.27 year-1.

The cooperation and coordination in multi-robot systems is a popular topic in the field of robotics and artificial intelligence, thanks to its important role in solving problems that are better solved by several robots compared to a single robot. Cooperative hunting is one of the important problems that exist in many areas such as military and industry, requiring cooperation between robots in order to accomplish the hunting process effectively. This paper proposed a cooperative hunting strategy for a multi-robot system based on wolf swarm algorithm (WSA) and artificial potential field (APF) in order to hunt by several robots a dynamic target whose behavior is unexpected. The formation of the robots within the multi-robot system contains three types of roles: the leader, the follower, and the antagonist. Each role is characterized by a different cognitive behavior. The robots arrive at the hunting point accurately and rapidly while avoiding static and dynamic obstacles through the artificial potential field algorithm to hunt the moving target. Simulation results are given in this paper to demonstrate the validity and the effectiveness of the proposed strategy.

The cooperation between mobile robots is one of the most important topics of interest to researchers, especially in the many areas in which it can be applied. Hunting a moving target with random behavior is an application that requires robust cooperation between several robots in the multi-robot system. This paper proposed a hybrid formation control for hunting a dynamic target which is based on wolves’ hunting behavior in order to search and capture the prey quickly and avoid its escape and Multi Agent Deep Deterministic Policy Gradient (MADDPG) to plan an optimal accessible path to the desired position. The validity and the effectiveness of the proposed formation control are demonstrated with simulation results.

The otolith, found in both inner ears of bony fish, has mainly been used to estimate fish age. Another application that has been developing significantly in recent years, however, is the use of otolith shape as a tool for stock identification. Often, studies have directly used the shape asymmetry between the right and left otoliths. We tested the magnitude of directional asymmetry between the sagittal otoliths (left vs. right) of 2991 individuals according to their catch locations, and we selected species to evaluate whether directional asymmetry may itself be a tool to evaluate stock boundaries. Elliptical Fourier descriptors were used to describe the otolith shape. We used a flatfish, the common sole (Solea solea, n = 2431), from the eastern English Channel and the southern North Sea as well as a roundfish, the bogue (Boops boops, n = 560), from the Mediterranean Sea. Both species showed significant levels of directional asymmetry between the testing locations. The bogue otoliths showed significant asymmetry for only 5 out of 11 locations, with substantial separation between two large areas: the Algerian coast and the western part of the Italian coast. The sole otoliths showed significant asymmetry in the shape analysis (3.84%–6.57%), suggesting a substantial separation between two large areas: the English and French parts of the English Channel and the southern North Sea. Consequently, directional bilateral asymmetry in otolith shape is a potential new method for stock identification.

Hunting moving targets with random motions and behavior is a challenge for robotic systems, and it occupies a significant position in the research on coordination and cooperation in multi-robot systems. Cooperative hunting between robots is used in a wide range of fields such as industry, military, rescue and other fields. The aim of this paper is to present a new strategy for target hunting by means of a cooperative multi-robot system in two-dimensional space, especially moving targets with random and unexpected behavior. The strategy is inspired from the behavior of wolves in hunting, as it summarizes the roles of robots in the system in three roles: the leader wolf, the antagonist wolf, and the follower wolf. This diversity of roles contributed to improve the convergence performance of the algorithm and reduce significantly the pursuit time. The validity of this strategy is supported by computer simulations.

Otolith shape analysis is an efficient fish stock identification tool. However, most applications used left and right otoliths or only one of them arbitrarily chosen without testing for biases resulting from potential directional bilateral asymmetry (DA) in otolith shape, i.e. a unimodal population-level deviation form bilateral symmetry between right and left otolith shapes. In this study, 560 bogues (Boops boops) were sampled from 11 geographical locations from the Canary Islands to the Aegean Sea and elliptical Fourier descriptors were used to describe their otoliths' shape. First, a significant otolith DA was observed at the global scale with an average amplitude of 2.77%. However, at the scale of sampling locations, DA was not always significant and varied in amplitude and direction. Second, population structure was investigated using the shape of either right otoliths or left otoliths or both together. Analyses based on right otoliths or both otoliths together, suggested three stock units: a North-Western Mediterranean Sea stock, an Eastern Mediterranean Sea stock, and a Central-Eastern Atlantic Ocean and South-Western Mediterranean Sea stock. In contrast, no coherent geographical pattern was found based on left otoliths. Our results highlight the importance of accounting for potential otolith DA in otolith shape-based stock identification.

Age, growth and mortality of the Starry weever Trachinus radiatus were studied for the first time from 214 individuals collected in the Gulf of Tunis between February 2014 and January 2016. The significant relationship between length-weight was observed for males (a = 0.011, b = 2.992, R-2 = 0.981, n = 77) and females (a = 0.010, b = 3.036, R-2 = 0.957, n = 109). Age was estimated by the observation of otoliths transverse thin sections. Age of individuals ranged from 1 to 15 years. The precision was measured by two age estimations from two experts and indicated a good agreement between them (PA = 85.6%, CV = 3.8% and IAPE = 4.1%). The growth parameters of the von Bertalanffy model were TL infinity = 38.41 cm, W-infinity = 507.47 g, K = 0.3396 year(-1), t(0) = 0 year for males and TL infinity = 45.46 cm, W-infinity = 914.04 g, K = 0.2136 year(-1), t(0 )= 0 year for females. Age at first sexual maturity (t(m)) of T. radiatus was 3.5 years, while the age at optimum length (t(opt)) was 6.6 years. The natural mortality (M), total mortality (Z), fishing mortality (F) and exploitation (E) rates were respectively M = 0.429 yr(-1), Z = 0.453 yr(-1), F = 0.024 yr(-1) and E = 0.053.

The present work provides length-weight relationships (LWRs) of 22 of the commercial fish species from the Northern Tunisian coasts. The sampling was done between April and May 2016 from the commercial landings in the Gulf of Tunis. The b value of the studied samples varied between 2.578 and 3.281. This work provides the first results about length-weight relationships of 15 species among 22 fishes studied in the Gulf of Tunis. This study presents the most recent and the broadest analysis of the LWRs for the following studied species; Zosterisessor ophiocephalus, Symphodus tinca, Sparisoma cretense, Scorpaena elongata, Scorpaena notata, Scorpaena porcus, Scorpaena scrota, Helicolenus dactylopterus, Serranus cabrilla, Serranus scriba, Boops boops, Diplodus annularis, Diplodus puntazzo, Pagellus erythrinus, Sarpa salpa, Spicara maena, Spicara smaris, Synodus saurus, Chelidonichthys lastoviza, Chelidonichthys obscurus, Trigla lyra and Uranoscopus scaber.

The occurrence of a single specimen of the Lessepsian migrant fish Pteragogus trispilus Randall, 2013 is reported for the first time off the Tunisian coasts. This new record extends westwards its area of distribution in the Mediterranean Sea. Species taxonomic status and hypothesis about its success of establishment are discussed.

Trachinus radiatus is a by-catch species on the Tunisian coasts. In this work, several aspects of its reproductive biology were investigated for the first time at local and worldwide scale. The studied sample was composed of 214 specimens with a total length ranging from 11.0 to 50.7 cm and was caught in the Gulf of Tunis. The sex-ratio was 1:1.42, with a significant difference between the number of males and females. Following the monthly variations of the mean gonadosomatic index (GSI), the sexual activity period of the starry weever occurred between May and September. Monthly mean hepatosomatic index (HSI) varied in exactly the same way as the GSI. The best condition of the starry weever was recorded between April and September. The evaluated length at first sexual maturity (TL50) of the species was 24.5 cm. For an optimal protection of T. radiatus, it should be caught between the length range of TL50 = 24.5 cm and L-opt = 35.0 cm.