Evolutionary impact assessment is a framework for quantifying the effects of harvest-induced evolution on the utility generated by fish stocks.

Samples of Atlantic sardine Sardina pilchardus (also known as European pilchard) were collected bimonthly from 2004 to 2008 off the central west coast of Portugal to describe the reproductive activity of this indeterminate batch‐spawning species; compare the seasonality of somatic growth, condition, and feeding; and evaluate differences between sexes. Monthly assessments of individual biological information for both males and females were complemented by histological analysis of ovaries during 1 year and liver tissues (both sexes) at different times of the reproductive cycle. The temporal patterns of the gonadosomatic index and various histological indices (most advanced oocyte stage, atresia incidence and prevalence, and spawning activity) indicated that Atlantic sardine were reproductively active mainly from October to March and that residual activity occurred in the remaining months. For both sexes, condition indices (hepatosomatic index, relative weight, and amount of fat stored) increased mainly during spring, reached a maximum at the end of summer just before the subsequent spawning season began, and then decreased during autumn and winter, declining to minimum levels at the beginning of spring coincident with a significant reduction in reproductive activity. Somatic growth took place mainly during spring and early summer for both sexes. The observed seasonal patterns in these biological properties suggest a seasonal transition from a period in which energy resources are allocated to reproduction (autumn and winter) to a period in which resources are allocated to growth and fat deposition (spring and summer). The only exception was the distinct hepatosomatic index pattern and the histological differences in hepatocytes between males and females during the spawning season, which may be related to the dual function of the liver in females (lipid metabolism and yolk precursor synthesis).

We investigate spatial and temporal variations in sardine maturation patterns and discuss the implications for stock structure, using recent samples collected opportunistically across the species range and data collected regularly for the assessment of the Atlanto-Iberian stock. Maturity ogives were fitted to maturity-at-length data using Generalized Linear Models, and maturation patterns are summarized by length at first maturity (L50). Sardine attain sexual maturity at a total length of 10.9–16.8 cm. The percentage of mature small sardine increases from north to south across the Northeast Atlantic. L50 is low in the Mediterranean and Moroccan waters, but maturation is delayed towards the limits of the species' range. Sardine mature smaller in the Gulf of Cadiz than in other areas of the Atlanto-Iberian stock, although there is no indication of a different maturation pattern north of the stock boundary. These results are not sufficient to review the stock structure of sardine, but question the hypothesis of homogeneous biological properties of sardine populations within the stock area. Sardine maturation length reduced and the spawning period extended in western Iberia during the past two decades. Associated increases in fish condition and fat reserves during the summer feeding season suggest that variations in reproductive traits may have been caused by environmentally driven changes in food availability.

During the past decade, regional changes in the dynamics of the Atlanto-Iberian stock of sardine, and its exploitation by Portuguese and Spanish purse-seine fisheries, have increased the uncertainties in estimated trends of spawning biomass, stock abundance, and fishing mortality. Together with recent evidence for lack of discontinuities in the distribution of sardine eggs at the edges of the stock area, this casts doubts on the hypothesis that the stock is a panmictic, closed population. Sardine morphometric data (truss variables and landmark data) from 14 samples spanning the northeastern Atlantic and the western Mediterranean were analysed by multivariate and geometric methods. The analyses explored the homogeneity of sardine shape within the area studied, as well as its relation to that of adjacent and distant populations (Azores and northwestern Mediterranean). Principal components analysis on size-corrected truss variables and cluster analysis of mean fish shape using landmark data indicate that the shape of sardine off southern Iberia and Morocco is distinct from the shape of sardine in the rest of the area. The two groups of sardine are significantly separated by discriminant analysis, and their validity was confirmed by large percentages of correct classifications of test fish (87 and 86% of fish from the test sample were correctly classified into each group, respectively). There was also some evidence that fish from the western Mediterranean and the Azores form a separate morphometric group. These results question both the homogeneity within the Atlanto-Iberian sardine stock and the validity of its current boundaries.

The World Conference on Stock Assessment Methods (July 2013) included a workshop on testing assessment methods through simulations. The exercise was made up of two steps applied to datasets from 14 representative fish stocks from around the world. Step 1 involved applying stock assessments to datasets with varying degrees of effort dedicated to optimizing fit. Step 2 was applied to a subset of the stocks and involved characteristics of given model fits being used to generate pseudo-data with error. These pseudo-data were then provided to assessment modellers and fits to the pseudo-data provided consistency checks within (self-tests) and among (cross-tests) assessment models. Although trends in biomass were often similar across models, the scaling of absolute biomass was not consistent across models. Similar types of models tended to perform similarly (e.g. age based or production models). Self-testing and cross-testing of models are a useful diagnostic approach, and suggested that estimates in the most recent years of time-series were the least robust. Results from the simulation exercise provide a basis for guidance on future large-scale simulation experiments and demonstrate the need for strategic investments in the evaluation and development of stock assessment methods.