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In this paper, we discuss the costs and benefits, in relation to economics and Alaska's salmon management policies, associated with two management strategies on the Egegik and Togiak sockeye salmon ( Oncorhynchus nerka) fisheries in Bristol Bay, Alaska. 'Daily management' allows managers to open or close the fishery on a daily basis, whereas a fixed fishing schedule allows fishing, to the extent practical, on fixed days of the week. To compare the strategies, we simulated the effects of daily management and a fixed fishing schedule on the two fisheries. Our simulations show that a daily management strategy results in higher yearly catches, less yearly variation in escapement, and fewer years of escapement below the goal range. A fixed fishing schedule results in less yearly variation in catch and a more stable harvest rate, with the harvest stability more pronounced when effort was held constant. Daily management is a desirable strategy for fisheries that are managed for maximum sustainable yield, have high fishing effort, have a small fishing area, or have a more temporally compressed run. A fixed fishing schedule is a desirable strategy for fisheries with less intense effort, budgetary or efficiency concerns, or stock components that differ in run timing. [ABSTRACT FROM AUTHOR]

The effective sampling volume of trawl and acoustics is an important parameter in fish abundance estimation surveys. This paper presents a method to compute the probability of a fish being available to the bottom trawl and the probability of it being seen on the echo sounder, given its initial position relative to the vessel path. These probabilities are then related to the calculation of the effective observational volume for trawl and acoustics, the two main tools of measuring abundance of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). As an example, the computation is carried out for a typical vertical distribution in the Barents Sea. Our model is based on an Ornstein–Uhlenbeck model for the fish swimming trajectories, and its parameters are estimated using observations of swimming trajectories for individual fish, recorded by a split-beam echo sounder. The model itself constitutes a general method to translate observations on behaviour of individual fish to probability maps. The results indicate a typical fishing height of 20 m for the bottom trawl, but it is also shown that there is a relatively low probability of catching by the trawl what you see on the echo sounder, even for fish positioned directly in the trawl path. This is because of strong lateral movements of the fish. [ABSTRACT FROM AUTHOR]

Biological invasions continue to accelerate, and there is a need for closer integration between invasive species research and on-the-ground management. In many regions, aquatic invasive species have established isolated populations, but have not yet spread to many sites that provide suitable habitat. In the Laurentian Great Lakes region, several Great Lakes invaders such as zebra mussel (Dreissena polymorpha), rainbow smelt (Osmerus mordax), and spiny water flea (Bythotrephes longimanus) are currently undergoing secondary spread to the smaller inland lakes and streams. This paper describes recent advances in forecasting the secondary spread of aquatic invasive species and presents a framework for assessing vulnerability of inland waters based on explicit assessment of three distinct aspects of biological invasions: colonization, site suitability, and adverse impact. In many cases, only a fraction of lakes on the landscape are vulnerable to specific invasive species, highlighting the potential application of this type of research for improving invasive species management. Effective application to on-the-ground resource management will require that research aimed at assessing site vulnerability be translated into management tools. [ABSTRACT FROM AUTHOR]

This paper describes how multinomial models can be used to study developmental rates of biological processes and how these are affected by different factors such as temperature or parental effects. First, the most common multinomial models for ordinal categorical data (namely, proportional odds, continuation-ratio, and extended continuation-ratio models) are described within the particular framework of developmental rates for discrete and ordered stage classified biological processes. Then, the extraction from the fitted models of a series of biologically meaningful parameters is proposed. In particular, maximum probable age and several alternative definitions for stage duration are presented and pros and cons of each of them are discussed. As an example, the methodology is applied to analyze the temperature dependent development of anchovy (Engraulis encrasicolus) eggs in the Bay of Biscay. [ABSTRACT FROM AUTHOR]