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Abstract Relative growth in crustaceans is a topic of quite high importance that allows, among other things, to estimate their size at the onset of morphometric sexual maturity. In this process, it is usual to start from a transition point and then generate regressions that reflect phases of the sexual development of the individuals (i.e., mature and immature). There are several statistical methods that allow data to be classified into subsets, but according to the specific growth pattern at issue, those methods may or may not be usable. This paper proposes a simple method to classify data into two subsets, viz., when they are overlapping over a wide range of sizes. The actual procedure consists of a linear regression that divides the data. Subsequently, a linear regression is applied to the groups generated by adjusting the parameters through maximum log-likelihood. The observed values will be classified according to the smallest residual difference generated with each regression line. The proposed method was tested by separating the sexes of Goyazana castelnaui, using real data. The efficiency of the method was analysed based on the percentage value between the number of total data and the number of correctly classified data. Additionally, the k-mean cluster was used as a conventional method, the results of which were reclassified by a linear discriminant analysis. The efficiency of the proposed method was >80% while that of the conventional method was >60%. The values misclassified by the proposed method were mixed with those of the opposite sex, so it was expected to fail in those cases. The proposed method is a simple alternative that can serve as a basis for subsequent morphometric analysis, especially for acquiring an initial insight in the structure of a dataset collected for a study of relative growth.

The objective of this paper was to characterize bycatch in an experimental fishery for Patagonian toothfish in Ecuador during 2017–2021. Diversity was analysed using Shannon, Margalef, Simpson, and Dominance indices. Bycatch representativity was calculated as the difference percentage between the target catch and non-target, in weight. The bycatch comprised 51 taxa and was composed primarily of fish. In addition, 12 species of pelagic habits (i.e. fishes and sharks) were also captured during the deployment/retrieval of fishing gear. The most frequent species (by number of individuals) were chimaeras (Hydrolagus melanophasma), grenadiers (Antimora rostrata, Coryphaenoides delsolari, and Coryphaenoides armatus), and sharks (Etmopterus granulosus and Centroscymnus owstonii). The diversity was medium low, according to the Shannon indices (0.5–1.8), with a negative trend for dominance and a positive trend for equitability.

Panulirus penicillatus is a lobster species primarily found in insular regions but also recorded in coastal continental zones of various countries along the American Pacific. This study reports P. penicillatus for the first time in the coastal area of Manabí Province, mainland Ecuador. Previously, its presence was known only in the Galápagos Islands, where it is a commercial species. The record is based on two adult individuals of P. penicillatus, both collected in October 2023 from fishing activities, one through nighttime apnea diving and the other via artisanal fishing using a gillnet. Panulirus penicillatus es una langosta de presencia principalmente insular, pero también con registros en zonas costeras continentales de diferentes países del Pacífico americano. En este trabajo se reporta por primera vez a P. penicillatus en la zona costera de la provincia de Manabí, Ecuador continental. Antes de este reporte solamente se conocía su presencia en las islas Galápagos, donde es una especie comercial. El registro se basa en dos individuos adultos de P. penicillatus, ambos recolectados en octubre del 2023 de la pesca, uno mediante buceo nocturno bajo la modalidad de apnea y el otro en la pesca artesanal utilizando red de enmalle.

Ucides occidentalis es un cangrejo de importancia pesquera en Ecuador. El objetivo del presente trabajo fue estimar su abundancia en un área de uso y custodia de manglar, en el Golfo de Guayaquil, Ecuador. La abundancia fue representada por la densidad y el tamaño poblacional, determinados conforme el muestreo por distancias utilizando transectos de puntos. Un total de 38 puntos fueron establecidos, basados en un muestreo no-probabilístico de oportunidad. Los individuos fueron recolectados por pescadores locales. Cada cangrejo fue sexado y su talla (i.e., ancho de cefalotórax-AC) registrada con un calibrador Vernier. Se determinó la proporción sexual, talla media, densidad y tamaño poblacional. La proporción sexual indica un número ligeramente superior de hembras (1:1,10). La talla media poblacional fue 7,47 cm AC; los machos presentaron una talla superior (7,69 cm AC) referente a las hembras (7,33 cm AC). La densidad poblacional fue 0,27 ind/m2 y el tamaño poblacional estimado fue de 743670 individuos. La mayor densidad la presentaron las hembras, seguidos de los machos comerciales (> 7,5 cm AC). Los machos no-comerciales (<0,75 cm AC) tuvieron una abundancia baja (0,03 ind./m2). La proporción sexual difiere entre los reportes previos, lo cual podría relacionarse con la prohibición de capturar hembras en Ecuador, que ocasiona una mayor presión pesquera sobre los individuos machos. La abundancia de U. occidentalis es inferior a lo reportados por otros autores (i.e., 0,61-1,2 ind./m2), lo cual debe ser tomado con cautela debido a las diferencias en las metodologías empleadas.

Growth estimates of animals are often based on a single data set. The sizes used to determine these estimates can nevertheless be biased by the selectivity of the data source and how well the data represent a population. The average growth of the brachyuran crab Ucides occidentalis (Ortmann, 1897) (Ocypodidae) had been previously estimated utilizing data derived from either commercial catch or scientific field data, consequently generating conflicting results. We determined the average growth of male U. occidentalis by analyzing commercial catch data alone and, subsequently, estimated average growth from a combination of the same commercial data with scientific data collected in situ in mangrove areas (i.e., combined data). Size frequency distributions were constructed using Kernel density estimators, characterizing the modes as Gaussian components. A multi-modal approach was used to select one of five growth models (asymptotic, non-asymptotic, and versatile) that most closely represented the average growth estimated from both cohorts of combined data, which had previously been identified through modal progression, and commercial data. The case 1 of the Schnute model was selected as the best model by Akaike Information and Bayesian Information criteria for both commercial and combined data sets. A convex growth curve was generated for the commercial data (asymptotic growth), whereas an inverted vertical sigmoidal curve was generated for the combined data (non-asymptotic growth). The data sets differed in that commercial data were represented by adult individuals, whereas the combined data included juveniles and adults. This difference significantly affected the average growth estimates calculated for each data set. The growth pattern of male U. occidentalis is best described by a non-asymptotic growth curve, which is consistent with that reported for females of this species.

Sexual dimorphism was established in Ucides occidentalis (Ortmann, 1897) in the Gulf of Guayaquil, Ecuador on the basis of the size and dimensions of the chelar propodus (CP); whether the CP can be used as an indicator of sexual maturity in males was also evaluated. Morphological differences were also established in individuals by inspecting CP variability. Morphotypes were identified as homochelous (HmC, having a similar CP) or heterochelous (HtC, having one CP larger than the other), and varieties were established by the differences in the CP dimensions of each morphotype. The Kruskal-Wallis test was used to determine whether significant size differences based on the length and height of the major chelar propodus for each morphotype exist between the sexes. The largest sizes were determined in males (p<0.01), and there was a significant difference (p<0.01) in length and height when the males of each morphotype were compared. This study established that U. occidentalis exhibits allometric CP growth, because the small sizes in successive molts do not allow the observation of evident differences between the developmental stages (juveniles and adults). Therefore, sexual maturity cannot be estimated in males using the CP, and it is necessary to use other structures (e.g., the pleopods) or methodologies (e.g., physiological) to estimate sexual maturity.

El estudio compara dos métodos de estimación (i.e., cuadrantes y distancias) de densidad poblacional, en O. gaudichaudii. Se establecieron 13 transectos en la playa “Los Ranchos” y ocho en “Las Bocas”; además, se realizó un censo visual en cada playa. Los análisis se desarrollaron considerando a Los Ranchos como un área y como dos subdivisiones (Los Ranchos-1, 2). Los resultados mostraron que, el muestreo por cuadrantes fue más preciso, en Los Ranchos-2 (6% de sesgo) y Las Bocas (4% de sesgo) mientras que, el muestreo por distancias fue más preciso en la playa Los Ranchos (32% de sesgo) y Los Ranchos-1 (29% de sesgo). En playas con altas densidades (más de 0,5 ind./m2) se debe seleccionar el método por cuadrantes y en playas con bajas densidades (menos de 0,5 ind./m2) se recomienda el método por distancias. The study compares two methods (i.e., quadrants and distances) for estimation of population density in O. gaudichaudii. On the beach “Los Ranchos”, 13 transects were established and eight in “Las Bocas”; in addition, a visual census was carried out on each beach. In the analyses Los Ranchos was considered as an area and as two subdivisions (Los Ranchos-1, 2). The results showed that, the sampling by quadrants was more precise in Los Ranchos-2 (6% of bias) and Las Bocas (4% of bias) while, the distance sampling was more accurate in Los Ranchos beach (32% of bias) and Los Ranchos-1 (29% of bias). In beaches with high densities (more than 0,5 ind./m2) the method by quadrants should be selected and on beaches with low densities (less than 0,5 ind./m2) the method by distances is recommended.

The record is based on two adult individuals of P. penicillatus, both collected in October 2023 from fishing activities, one through nighttime apnea diving and the other via artisanal fishing using a gillnet. Genetic isolation between the Western and Eastern Pacific populations of pronghorn spiny lobster Panulirus penicillatus. Life history of the red spiny Lobster, Panulirus penicillatus (decapoda: Ecology of Juvenile and Adult Palinuridae (Spiny Lobsters).

Ucides occidentalis (Ortmann, 1897) is a commercial crab in the Ecuadorian continental coast, however, little knowledge is available about its biology. A very important aspect for stock assessment and fisheries management is the species' individual growth. In this paper U. occidentalis growth in males and females was determined by indirect methods and the multi-model approach. By Kernel density estimators size frequency distributions were built, separating their Gaussian components by the Bhattacharya's method. Using modal progression, the cohorts were identified, and one was selected to apply asymptotic, non-asymptotic, and Schnute's versatile growth models. The best fit model was selected using the Akaike and Bayesian weights. Case 1 of Schnute was the winner model in both sexes, asymptotic in males with L∞=93.62 mm cephalothorax width (CW), k=0.57 year−1 and t0=−0.02 year−1, but it was non-asymptotic for females with an inflexion point in 2.49 years that corresponded to 73.72 mm CW. The type of individual growth of this species varies between sexes, which may be linked to reproductive issues; however, we should consider the data source and their impact on the interpretations that we can draw about individual growth. Therefore, for future studies, using other sources of information such as commercial catches or capture-recapture to validate the results presented, is recommended.