Title: Developing Model-based Fishery-Independent and Fishery- Dependent Abundance Indices for Southern Horse Mackerel (Trachurus trachurus) in ICES Division 9a
University that offers the project: University of Vigo
Director: Rodríguez Álvarez, María José
Student: Jácome Barrantes, Gustavo Andrés
Summary:
Reliable abundance indices are fundamental for robust stock assessments and sustainable fisheries
management. The reliablity of stock assessment results mostly depends on the quality, accuracy
and consistency of both fishery-independent and fishery-dependent data used to monitor population
changes over time (Hilborn & Walters, 1992; Maunder & Punt, 2004. The Southern horse mackerel
(Trachurus trachurus) is currently managed as a single stock unit in the waters of the western Iberian
Peninsula (ICES Division 27.9.a).
Traditionally, fishery-independent surveys have relied on design-based estimates derived from standardized
sampling schemes. However, the development of model-based approaches have become
increasingly important in fisheries and ecosystem research as they provide a more flexible and realistic
way to describe population dynamics. These approaches can better account for complex spatial
and temporal patterns, frequent zero catches ,variation in sampling effort, and environmental effects
on species distribution.. The current stock assessment for Southern horse mackerel has a main
fishery-independent index derived from the Spanish and Portuguese bottom trawl surveys.. While
this survey provides valuable information, the combining data from additional fishery-independent
surveys may improve the spatial coverage and representativeness of the stock distribution across
Iberian waters (Lo et al., 1992; Stefánsson, 1996; Thorson, and Haltuch , 2019)
In addition to fishery-independent surveys, fishery-dependent data is one of the most important and
widely available sources of information for stock assessments. When properly standardized, commercial
catch and effort data can provide valuable insights into temporal and spatial changes in
stock abundance. Standardized Landings per Unit of Effort (LPUE) indices derived from commercial
fisheries can complement scientific survey data, in particular, can complement scientific survey
data by providing information on components of the stock that may be poorly represented in fisheryindependent
sampling.. In this context, there is particular interest in developing an index that specifically
targets older age groups within the mature population. Such an index could improve our
understanding of long-term population trends and contribute to more reliable stock assessments and
management.
This proposal aim to 1) develop a model-based standardized abundance index by combining information
from the Portuguese, the Spanish Bottom Trawl Survey in the Gulf of Cádiz, and the North
Spanish Bottom Trawl Surveys within a unified spatio-temporal framework. 2) evaluate and compare
different approaches to standardize LPUE using fishery-dependent data from the Spanish trawl fleet
operating in Atlantic Iberian waters.
The integration of fishery-independent survey indices and commercial LPUE indicators is expected to improve the characterization of stock dynamics and provide more robust inputs for stock assessment.
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