Stocking effects on a fish population growth with time lag regulation.

The movement of fish in watersheds is frequently inhibited by human-made migration barriers such as dams or culverts. The resulting lack of connectivity of spatial subpopulations is often cited as a cause for observed population decline. We formulate a matrix model for a spatially distributed fish population in a watershed, and we investigate how location and other characteristics of a single movement barrier impact the asymptotic growth rate of the population. We find that while population growth rate often decreases with the introduction of a movement obstacle, it may also increase due to a ‘retention effect’. Furthermore, obstacle mortality greatly affects population growth rate. In practice, different connectivity indices are used to predict population effects of migration barriers, but the relation of these indices to population growth rates in demographic models is often unclear. When comparing our results with the dentritic connectivity index, we see that the index captures neither the retention effect nor the influences of obstacle mortality. We argue that structural indices cannot entirely replace more detailed demographic models to understand questions of persistence and extinction. We advocate the development of novel functional indices and characteristics.

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A System Dynamics Model for a Sustainable Fish Population

International Journal of Technology Diffusion ◽

10.4018/ijtd.2014040104 ◽

2014 ◽

Vol 5 (2) ◽

pp. 39-53 ◽

Cited By ~ 3

Author(s):

Nayem Rahman

Keyword(s):

Population Growth ◽

System Dynamics ◽

Real World ◽

Mental Model ◽

Fish Population ◽

System Dynamics Model ◽

Dynamics Model ◽

Reasonable Approach ◽

Growth Stocks ◽

Real World Problems

To visualize or address complex real world problems, eliciting and mapping of a mental model is reasonable approach but it is far from sufficient by itself. In this article we present a system dynamics model. The purpose of the model is to develop a sustainable model for fish population, growth, and harvesting. The model was run through several important tests to determine its sensitivity to changing in key parameters and initial values with different scenarios and boundary conditions. Model results show that fish birth, growth, stocks and catch can be controlled quickly in different real-world changing conditions to maintain a sustainable fish population.

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COMPARISONS OF ESTUARINE MANAGEMENT NEEDS OF A TROPICAL PACIFIC MEXICAN HARBOUR AND A TEMPERATE CALIFORNIA HARBOUR

Marine Research in Indonesia ◽

10.14203/mri.v19i0.370 ◽

2018 ◽

Vol 19 ◽

pp. 21-38 ◽

Cited By ~ 1

Author(s):

Dorothy F. Soule ◽

Penny A. Morris ◽

John D. Soule

Keyword(s):

Water Quality ◽

Population Growth ◽

Historical Development ◽

Southern California ◽

Fish Population ◽

Economic Importance ◽

Thermal Gradients ◽

Point Conception ◽

Estuarine Management ◽

Excessive Nutrients

Two areas of the eastern Pacific are compared, the southern California wetlands south of Point Conception and Mazatlan, Mexico. The historical development of both areas is important in considering their present biological status. Southern California has been subjected to intensive population growth and urbanization while Mazatlan has remained relatively unchanged. Both areas are compared biologically in regards to the fish population, thermal gradients in the harbors, salinity, nitrate, nitrite and phosphate distributions. The economic importance of the harbors is recognized, however it is essential that measures are taken to restore or retain existing wetlands that are associated with the harbors. The harbors can serve as shelters for various organisms if water quality can either be maintained (as in the case of Mazatlan) or improved, and if input of toxic and excessive nutrients is limited.

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