Relaciones talla-peso de 15 especies de crustáceos mesopelágicos capturados durante campañas exploratorias frente a las Islas Canarias (Atlántico Centro Oriental)

Length-weight relationships (LWRs) were estimated for 15 mesopelagic shrimp species off the Canary Islands (central eastern Atlantic). Total length, cephalothorax length and total weight were taken for individuals collected during three research campaigns using a commercial semi-pelagic trawl net. The most represented families among the collected species were Sergestidae and Oplophoridae, with eight and three species, respectively. Overall, 60% of the species showed isometric growth, 33.3% negative allometry and 6.7% positive allometry. These 15 LWRs are the first contribution on mesopelagic shrimp species from the northwest Africa region, contributing to knowledge on the relative growth of these crustaceans.Se estimaron las relaciones talla-peso (LWR) para 15 especies de crustáceos mesopelágicos de las Islas Canarias (Atlántico Centro Oriental). Se tomaron la longitud total (TL), la longitud del cefalotórax (CL) y el peso total (W) de los individuos recolectados durante tres campañas de investigación utilizando una red de arrastre semipelágica comercial. Las familias más representadas entre las especies colectadas fueron Sergestidae y Oplophoridae con ocho y tres especies, respectivamente. En general, el 60% de las especies presentó crecimiento isométrico, el 33,3% alometría negativa y el 6,7% alometría positiva. Estas 15 LWR son la primera contribución para estas especies de crustáceos mesopelágicos de la región del noroeste de África, contribuyendo a aumentar el conocimiento sobre el crecimiento relativo de estos crustáceos

Life History Parameters and Fishing Aspects of the Alien Nimble Spray Crab <i>Percnon gibbesi</i> in a Native Area of the Central-East Atlantic

Percnon gibbesi is a native crab species characteristic of intertidal and subtidal zones of the Atlantic coast of the European Macaronesian archipelagos (Azores, Madeira, and Canary Islands), and probably also in the neighbouring rocky coasts of northwest Africa. P. gibbesi is considered an invasive alien species in almost all of the Mediterranean, with expanding populations from Spain to Turkey, including Libya; However, its biology and ecology are highly unknown, despite all its range of distribution. In the intertidal zones of Gran Canaria Island, this crab, in the intertidal zones of Gran Canaria Island, shows a carapace length range between 4.1 and 22.7 mm (4.1–22.7 in males and 5.7–22.3 in females), where females showed higher weights and lengths than males on average; However, males predominated in all samples, with a sex ratio of 1:0.57. The L∞ for this crab was estimated to be 27 ± 3 mm (23 ± 4 mm for females and 25 ± 4 mm for males). The growth coefficient (K) was 0.24 year−1, the total mortality (Z) was Z = 1.71 year−1, and the natural mortality (M) was 0.47 year−1. Although females grow faster than males, males are more abundant in the larger length classes. Although the presence of ovigerous females indicated that reproduction takes place twice a year, from March to April and from August to September, the number of cohorts detected by the modal progression analysis showed that reproduction takes place all year

Age validation in early stages of Sepia officinalis from beak microstructure

This is the first study addressing validation of the early growth stages (including the first increment) in the beaks of juvenile cuttlefishes. The age validation in juveniles of Sepia officinalis was performed by comparison of the number of increments observed in the rostrum surface of lower jaws with their true age. A total of 159 individuals were reared at 18 ºC and 21 ºC, with ages up to 31 days from hatching. The number of growth increments in the beak was counted and contrasted with the days of life after hatching, validating the hypothesis of one increment of growth corresponding to one day of life. The mean coefficient of variation between readings (measuring precision) was 2.95 ± 5.98%. The growth of the reading area (rostrum surface) and the periodicity of increment deposition showed no difference between the two culture temperatures and therefore daily deposition was confirmed at these temperatures.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Guerra-Marrero was supported by a PhD-fellowship (PIFULPGC-2017-CIENCIAS-2) from the University of Las Palmas de Gran Canaria.Peer reviewe

Age, growth, and population structure of the African cuttlefish Sepia bertheloti based on beak microstructure

In this study, we explored the feasibility of using the beaks of the African cuttlefish Sepia bertheloti for age estimation and growth analysis. The rostrum sagittal section (RSS) of the lower beak was the most suitable region in the species. It was applied in samples caught off Morocco and Guinea-Bissau between June 2018 and January 2020. A maximum life expectancy of around 14 months was observed (specifically 419 days for cuttlefishes from Morocco and 433 from Guinea-Bissau). The males presented greater longevity, as the maximum age of the females was between 9 and 11 months. Sepia bertheloti showed a negative allometric growth; however, the exponential model better describes each population growth. By sexes, the males of both locations followed an asymptotic growth model while the females exhibited a non-asymptotic growth. The growth rates were different between locations, with the highest values in Guinea-Bissau. The males, in turn, grew faster for both study locations. In Guinea-Bissau, these growth differences were influenced by the hatching season since individuals born between autumn and winter were the fastest-growing. Samples from Morocco did not show growth differences between the hatching season and other seasons. These results indicate that the RSS of lower beaks are suitable for estimating the age, growth pattern, and population structure of Sepia bertheloti.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Guerra-Marrero was supported by a PhD-fellowship (PIFULPGC-2017-CIENCIAS-2) from the University of Las Palmas de Gran Canaria.Peer reviewe

Aggregative Behaviour of Spiny Butterfly Rays (<i>Gymnura altavela,</i> Linnaeus, 1758) in the Shallow Coastal Zones of Gran Canaria in the Eastern Central Atlantic

The presence of spiny butterfly rays, Gymnura altavela, in waters less than 20 m deep off the Canary Islands shows marked seasonality, with relatively high abundances in the summer and autumn. Large aggregations of sometimes hundreds of individuals, primarily females, appear in specific shallow areas of the archipelago and seem to be associated with the seasonal variation in water temperature. This seasonal pattern of presence or absence in shallow areas suggests that spiny butterfly rays migrate into deeper waters or other unknown areas during the rest of the year. G. altavela shows sexual dimorphism; in our study, females were larger and more abundant than males, with a sex ratio of 1:18.9. The species’ estimated asymptotic length, L∞, was 183.75 cm and thus close to the common length reported for the species (200 cm). The von Bertalanffy growth constant (k) oscillated between 0.210 and 0.310 year−1, as similarly described for the species in the Western North Atlantic off the U.S. coast. From June to November, the seawater temperature oscillated between 19 and 24 °C, and massive aggregations of females occurred at 22–24 °C and in a few specific sandy beaches on the islands. Spiny butterfly rays, mostly females, show a preference for aggregating in shallow waters during summertime, probably conditionate to mating or breeding behaviour

First record of partial albinism in the critically endangered Angelshark ( Squatina squatina ) (Linnaeus, 1758)

We report the first case of partial albinism in the Critically Endangered angelshark, Squatina squatina. The encounter with this specimen took place while SCUBA diving on the beach of Tufia, located on the east coast of the island of Gran Canaria on 2 April 2021. This is also the first confirmed finding of an albino elasmobranch specimen in the Canary Island archipelago