Juan L. Valero

Feeding habits and prey selection by the skate Dipturus chilensis (Elasmobranchii: Rajidae) from the south-western Atlantic

The diet of Dipturus chilensis was composed mainly of the nototheniid fish Patagonotothen ramsayi , squid Illex argentinus , hake Merluccius hubbsi , serolid isopods, and crustaceans. Our results suggest that D. chilensis feeds selectively on some teleosts and rejects eel-like fishes. Total length of consumed P. ramsayi was significantly correlated with the skates mouth width.

Chapter 14 Dynamics, assessment and management of exploited natural populations

Publisher Summary This chapter discusses the dynamics, assessment, and management of exploited natural populations. All scallop stocks are structured as “metapopulations” in which subpopulations of sedentary post-larval individuals are connected with each other through the dispersal of pelagic larvae. The metapopulation is a useful conceptual framework for the analysis and management of benthic fisheries. Emphasis on spatial structure brings with it, the need to identify appropriate spatial scales for the observation, analysis and management of exploited scallop stocks. The hierarchy of spatial scales presented by Orensanz and Jamieson is adopted in the chapter. The primary factors tuning year-class-strength are those that affect advection and survival of pelagic larvae. These factors pertain largely to oceanographic conditions. It is natural that research on modulation of year-class-strength and the search for signs of climatic forcing focus on abundance indices aggregated at relatively large spatial scales. The empirical evidence about the influence of climate on larval availability and recruitment is considered. The transition between the two stages—namely, pelagic larvae and recruits is modulated by factors other than larval availability. The elusive relationship between aggregate spawning stock and recruitment is also discussed.

Chapter 26 Argentina

Publisher Summary This chapter discusses the two species, Aequipecten tehuelchus (Tehuelche scallop) and Zygochlamys patagonica (Patagonic scallop), their fisheries, and experimental results that have significance in the future development of aquaculture. The fisheries supported by these two species are radically different from each other. The Tehuelche scallop is the target of small inshore fisheries in the gulfs of northern Patagonia, and involves dredging and commercial diving. In spite of the small volumes landed, these fisheries are of considerable significance for the local economies. The Patagonic scallop fishery is an industrial operation conducted by three or four factory trawlers that process the catch at sea. Catches in the order of 50,000 tons yr -1 now rank this species among the most important scallop fisheries in the World. The Tehuelche scallop is a simultaneous hermaphrodite and is iteroparous. The Tehuelche scallop may do quick and brief swimming movements as an escape response to the predators or other disturbances.

ss3sim: an R package for fisheries Stock Assessment simulation with stock synthesis.

Simulation testing is an important approach to evaluating fishery stock assessment methods. In the last decade, the fisheries stock assessment modeling framework Stock Synthesis (SS3) has become widely used around the world. However, there lacks a generalized and scriptable framework for SS3 simulation testing. Here, we introduce ss3sim, an R package that facilitates reproducible, flexible, and rapid end-to-end simulation testing with SS3. ss3sim requires an existing SS3 model configuration along with plain-text control files describing alternative population dynamics, fishery properties, sampling scenarios, and assessment approaches. ss3sim then generates an underlying ‘truth’ from a specified operating model, samples from that truth, modifies and runs an estimation model, and synthesizes the results. The simulations can be run in parallel, reducing runtime, and the source code is free to be modified under an open-source MIT license. ss3sim is designed to explore structural differences between the underlying truth and assumptions of an estimation model, or between multiple estimation model configurations. For example, ss3sim can be used to answer questions about model misspecification, retrospective patterns, and the relative importance of different types of fisheries data. We demonstrate the software with an example, discuss how ss3sim complements other simulation software, and outline specific research questions that ss3sim could address.