Josué Martínez-Garmendia

Simulation analysis of evolutionary response of fish populations to size-selective harvesting with the use of an individual-based model

Abstract Many studies have been devoted to analyze data and/or discuss theory addressing the potential evolutive impacts of anthropogenic exploitation in fish populations. However, not many conclusions about the nature of long term changes in fish populations have been derived from wild population observations. Simulation models can help to identify factors that play important roles in the evolution of fish through genetic change. The objective of this paper is to present an individual-based model with a genetic component using parameters common to fish population dynamics. Such a model could help us gain insight in the impact of selective fishing mortality on the characteristics of the progeny through genetic based changes. The model deviates from quantitative genetics on its handling of trait inheritance. It also establishes a link between large scale population dynamic processes such as recruitment and the contribution of individual fish to the spawning stock biomass (SSB) and the resulting distribution of trait inheritance. The model uses parameter values for cod ( Gadus morhua ) from the literature to simulate four exploitation scenarios. The results indicate that smaller length-at-maturity, slower growth to smaller sizes and higher fecundity would be advantageous traits for adult survival under exploitation. However, the magnitude of such evolutive trend was very small with deterministic recruitment. Moreover, the effect of the selective forces determining the successful traits to be passed to the offspring was weakened even further under stochastic recruitment.

Hedging performance of shrimp futures contracts with multiple deliverable grades

The performance of the black tiger and white shrimp futures contracts traded in the Minneapolis Grain Exchange (MGE) is considered. These two futures contracts have suffered low trader participation[fn100] since their inception despite the underlying multibillion‐dollar cash shrimp market. The article tries to find answers for such lack of interest in the context of the multiple deliverable category character of both contracts. In particular, the hedging effectiveness and the adequacy of the premiums/discounts are measured for the various shrimp size categories traded in each contract. The analyses indicate that the hedging effectiveness of both contracts is relatively modest. Part of the explanation for the performance of the contracts resides in high deliverable category exchange option values, which stem from volatility in the price differentials between size categories. The fixed premiums/discounts are not able to provide a remedy to the alternation in the cheapest to deliver category. There is also a liquidity problem that could result from the peculiarities of seafood trade. It is concluded that the lack of trader interest may be influenced by initial high deliverable category exchange option values.

PREMIUMS/DISCOUNTS AND PREDICTIVE ABILITY OF THE SHRIMP FUTURES MARKET

Seafood futures contracts are a novelty in the derivative markets, having shrimp as their only exponent. Unfortunately, shrimp futures contracts have suffered a disappointing start. The analyses focus on testing whether premiums/discounts for non-par deliverable shrimp size categories can eliminate cash price differentials, and whether the shrimp futures market can predict cash prices without bias. Results indicate ineffective premiums/discounts and predictive bias. These results and the momentous changes taking place in the seafood industry are contrasted to discuss the viability of seafood futures contracts.