Multi-Annual Fluctuations in Reconstructed Historical Time-Series of a European Lobster (Homarus gammarus) Population Disappear at Increased Exploitation Levels

Andreas Sundelöf,Massimiliano Cardinale,Valerio Bartolino,Mats Ulmestrand,Fausto Tinti

doi:10.1371/journal.pone.0058160

Andreas Sundelöf, Massimiliano Cardinale + Show 3 more

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https://doi.org/10.1371/journal.pone.0058160

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Abstract

Through the history of ecology, fluctuations of populations have been a dominating topic, and endogenous causes of fluctuations and oscillations have been recognized and studied for more than 80 years. Here we analyzed an historical dataset, covering more than 130 years, of European lobster (Homarus gammarus) catches. The data shows periodic fluctuations, which are first dampened and then disappear over time. The disappearance of the periodicity coincided with a substantial increase in fishing effort and the oscillations have not reappeared in the time series. The shifting baseline syndrome has changed our perception of not only the status of the stock, but also the regulating pressures. We describe the transition of a naturally regulated lobster population into a heavily exploited fisheries controlled stock. This is shown by the incorporation of environmental and endogenous processes in generalized additive models, autocorrelation functions and periodicity analyses of time-series.

Highlights

Population fluctuations and their causes have been debated for almost a century (e.g. [1,2,3]) and are still a central topic for contemporary ecology (e.g., [4])
In this paper we present a unique time series of European lobster (Homarus gammarus) catches from the Skagerrak, eastern North Sea, developing from a lightly exploited to an overexploited phase (Figure 1)
The second source of data is from a number of lobster fishermen that have provided us with Voluntary Catch Diaries (VCD)

Summary

Introduction

Population fluctuations and their causes have been debated for almost a century (e.g. [1,2,3]) and are still a central topic for contemporary ecology (e.g., [4]). Causes of population fluctuations and their variability have been hypothesized to derive essentially from 1) environmental forcing (including anthropogenic forcing), 2) species interactions and 3) internal processes such as density dependent regulation of recruitment or survival. The theoretical underpinning of many population models suggest that high growth rates cause density dependent fluctuations [2,6]. The periodicity of oscillations is further sensitive to population structure [7]. In fisheries models such oscillations are maintained at a moderate-low fishing mortality and diminished at high fishing mortality [6]. Harvesting is generally damping oscillations but promoting fluctuations of populations with high growth rates

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