Optimization of fishing effort allocation and efficient deployment of fishing gear are necessary for successful management of multispecies fisheries. Campeche Bank, located in the southwestern Gulf of Mexico, provides an opportunity to understand fishing effort and fishing gear dynamics through the analysis of the fishing operations of a semi-industrial fleet and obtain insights into how to identify management units for these types of fisheries. We analyzed the operation of this fleet over 4 years by splitting it into groups and then fully describing the behavior of each one. Our analysis was based on two data sets, including records from logbooks (8,390 fishing trips) and interviews with skippers from fishing vessels at the landing ports (882 trips). We used multivariate statistical techniques (SIMPER, hierarchical cluster analysis, and nonmetric multidimensional scaling analysis) to define targeted species and define the groups (métiers). Geographical information systems tools helped us to identify the spatial distribution of fishing effort by gear on an annual and monthly basis. We identified four different groups that resulted from the combination of fishing gear, target species, and fishing zones. Shifting behavior between gears and target species was a fishing strategy developed by several vessels, and technological interactions were evident between two gear types that employ longlines. Spatial allocation of fishing effort indicated a preference for certain fishing zones by vessels that operated two of the four gears. This pattern was consistent throughout the years studied; however, monthly differences did exist. The results provide information to identify management units in multispecies fisheries through the identification of métiers and the understanding of fishing strategies.

The presence of transient and temporary individuals in capture-mark-recapture studies may violate the assumption on equal catchability, and thus yield biased estimates. We investigated the effects of residency patterns on population parameters of bottlenose dolphins inhabiting the coastal waters off the Alvarado Lagoon System (ALS), Veracruz, Mexico. We hypothesized that this population is open but there exists a “core community” that behaves as a closed population. Between 2006 and 2010, we conducted 75 photo-identification surveys and recorded 263 dolphin group encounters, in which 231 dolphins were identified. Individuals present during only one season, classified as transients (n= 85), were excluded from the study, and a standardized residency index (IH₄) was computed for each dolphin that remained in the sample (n= 146). We used the K-means clustering method to split the sample into groups based on individual (seasonal, annual) IH₄values. These clusters were named as regular residents (RR,n= 55), occasional residents (OR,n= 45), and occasional visitors (OV,n= 46). The cumulative frequency of newly identified individuals displayed an asymptotic trend for the whole sample and all clusters, indicating that most of the individuals present in the study area during the study period were identified. The assumption of demographic closure was tested to define the core community, and was rejected for the whole sample and the OV cluster (p< 0.001 in both cases), indicating that the population is open. The closure assumption was not rejected for RR and OR clusters (χ²= 6.88, DF = 13,p= 0.91, and χ²= 17.8, DF = 16,p= 0.33, respectively), indicating that these clusters were demographically closed over the 5-year period. Thus, we defined this aggregation of individuals as the “core community”. The closed population model M_thindicated that the total abundance of this core community was 123 individuals (95% CI: 114–133). Our results provide quantitative evidence of the existence of a core community in open waters of the Gulf of Mexico, and points toward residency pattern as a main driver of population dynamics. These results highlight the importance of considering residency patterns when dealing with heterogeneity in the sample of a highly mobile species.