Reproductive biology of female blue swimmer crabs in the temperate estuaries of south-eastern Australia

The blue swimmer crab (BSC, Portunus armatus) is an economically and culturally important species distributed throughout the coastal waters of the Indo-Pacific region. Reproduction of BSC is poorly understood in south-eastern Australia, a region that is experiencing substantial tropicalisation from global warming. We examined gonadal development, egg-mass relationships, and the influence of temperature on gonadal development and egg production within five different estuaries spanning ∼2.5° of latitude. A negative correlation between the gonadosomatic index (GSI, an index of gonadal development and reproductive investment) and hepatosomatic index (HSI, an index of energy storage) was observed in only the final stages of ovarian development. The weight of the egg mass increased logarithmically with body mass, accounting for up to 55% of total body mass, which was significantly larger than observed in other studies. Thermal performance curves showed a peak in individual reproductive output at a mean monthly temperature of ∼24°C, at which the individual egg mass weight reached a maximum and the HSI reached a minimum. Environmentally driven variation in BSC reproduction has implications for population productivity and inter-annual variation in recruitment

Ineffectiveness of light emitting diodes as underwater deterrents for Long-tailed Ducks Clangula hyemalis

Gillnet bycatch accounts for over 400,000 bird mortalities worldwide every year, affectinga wide variety of species, especially those birds that dive when foraging. Technologicalsolutions to improve gillnet visibility or deter birds from approaching nets, such as LEDlights, are essential for aiding diving birds to perceive nets as a hazard. Designing suchsolutions requires obtaining visual and behavioural ecology information from species toassess their ability to see the warning devices, and to examine their behavioural responsesto them. Seaducks, particularly Long-tailed DucksClangula hyemalis,have high bycatchmortality rates. We examined the visualfields of four Long-tailed Ducks to understandtheir three-dimensional view around the head. The visualfield characteristics of thisspecies indicate a reliance on visual guidance for foraging associated with their capture ofvaried, mobile prey in their generalist diet. We subsequently conducted dive tank trials totest the effectiveness of 12 different LED treatments as visual deterrents to the underwaterforaging behaviour of 8 Long-tailed Ducks. During each trial, ducks were offered foodrewards from a specific underwater location in a dive tank, having the choice of whether totake the food or not. At the same time, they were exposed to either one LED light or thecontrol (no light) to determine whether the presence of each light affected the foragingsuccess rate of dives compared to the control. Exposure of ducks to all 13 treatmentcombinations was randomised over the trial period. White lights with an increasingflashrate were shown to have a significant positive effect on foraging success, and likely acted asa visual attractant, rather than as a deterrent. No light treatment significantly reduced theforaging success of ducks. LED lights did not inhibit the feeding of Long-tailed Ducks. Suchlights may be ineffective as underwater visual deterrents when deployed on gillnets, whilewhiteflashing lights may make foraging sites more attractive to Long-tailed Ducks.©2020 The Authors. Published by Elsevier B.V. This is an open access article under the CCBY-NC-ND license

Design of PI controller with input constraint: application on blending process

Because of their simplicity, reliability and effectiveness, proportional–integral–derivative (PID) controllers remain the most widely used controllers in the process industries. Actuator saturation is among the most common and significant problem in control systems design. Normal PID controller does not take this into consideration. Normally, an anti‐windup compensator is employed in the system to overcome the problem. In this contribution, a new set of controller tuning relations is developed to tune the PI controller when the system is under saturation. The blending process was described as first order plus time delay (FOPTD) process and an expression is developed for saturation level, U as a function of controller gain, Kc with the range of R 0.4–2 (ratio of time delay to time constant). The proposed tuning rule relate the parameters of the controller to the parameters of a FOPTD model of the plant to a step change in the set point. The proposed method was applied to PI controller and tested on the process of blending system of sweetened condensed milk. The performance of the controller with various tuning formulae incorporated with classical anti‐windup strategies has been compared. The simulation results showed that the proposed method could give satisfactory performance in controlling the process