José Juan Castro

Catch-and-Release (C&R) is a widespread practice in recreational fisheries in which fish are released alive after capture. Its effectiveness, however, depends on maintaining high post-release survival to ensure management and conservation benefits. This study evaluated post-release mortality in bogue (Boops boops), a common target species in Mediterranean and Atlantic temperate fisheries, examining its relationship with several explanatory variables, with particular emphasis on the effect of de-hooker devices. Results indicated a post-release mortality rate of 20.4% (95% CI: 13.5-29.4%), largely associated with deep-hooking events. Mortality was significantly lower when hooks were manually removed from shallow locations (2.5%; 95% CI [0.1-14.7]) compared to line-cutting (29.4%; 95% CI [15.7-47.7]) and de-hooker use (32.4%; 95% CI [18-50.6]) in deep-hooking scenarios. No significant differences in mortality were detected between line cutting and the de-hooker treatment, suggesting that de-hookers perform similarly to line cutting in deeply hooked fish. Reflex impairment, especially loss of orientation, was identified as a strong predictor of mortality and was most frequent in deeply hooked individuals. Bleeding was also significantly associated with mortality, and the combined presence of bleeding and disorientation consistently resulted in lethal outcomes. Neither reflex impairment nor bleeding differed significantly between fish treated with de-hookers and those subjected to line-cutting, indicating that de-hookers do not mitigate physiological damage once deep-hooking has occurred. This study provides the first evidence that orientation impairment reliably predicts post-release mortality in bogue. Overall, preventing deep hooking is the most effective strategy to minimize mortality, while de-hookers provide survival outcomes similar to line-cutting in deeply hooked fish.

Despite the popularity of elasmobranchs in zoos and aquariums, data on hematological values for health monitoring remain limited, particularly for wild pop

Background: Despite the popularity of elasmobranchs in zoos and aquariums, data on hematological values for health monitoring remain limited, particularly for wild populations. In this study, reference intervals for key hematological parameters and blood pH were established from blood samples of 49 adult females of the Critically Endangered Spiny Butterfly Ray (Gymnura altavela) collected across three shallow beaches in the Canary Islands. Additional data were obtained from four adults maintained under human care. To our knowledge, this is the first report of hematological and blood pH reference intervals for free-ranging G. altavela. Results: Lymphocytes (56%) were the dominant leukocyte, followed by heterophils (23.6%), eosinophils (16.7%), monocytes (2%), neutrophils (1.1%), and basophils (0.2%). Median values included 356.6 × 103 cells/µL for red blood cell count (RBC), 31.7 × 103 cells/µL for white blood cell count (WBC), 28.2% for packed cell volume (PCV), and 8.1 g/dL for total plasma solids (TS). Blood pH averaged 7.25, rising to 7.38 with temperature correction. These values remained consistent across reproductive states and housing conditions, suggesting minimal physiological disruption. Conclusion:: This study highlights the effectiveness of rapid, low-stress sampling and provides essential baseline data to support veterinary care and conservation strategies for G. altavela. Expanding future research with a larger sample size will enhance understanding of health variations by age, sex, and reproductive status.

The size of individuals of the intertidal broad-clawed porcelain crab (Porcellana platycheles (Pennant, 1777)) shows great variability on the island of Gran Canaria, Canary Islands, Spain, with individuals significatively larger in the north than in the south of the island. Males showed higher carapace length and width as well as weight than females. Females predominated over males, with a sex ratio of 1:1.5. Ovigerous females were observed only from November to April, with a peak of abundance in January and a secondary one in April. The growth pattern of crabs varied from positive allometric (north and eastern coasts) to isometric (southern coast). Both sexes also showed different growth patterns, being positive allometric in males, negative allometric to isometric in females.

In the present study, the Atlantic or Telle’s harlequin shrimp, Gnathophylleptum tellei d’Udekem d’Acoz, 2001 (Palaemonidae), is shown to be a dietary echinoderm specialist, feeding on the tube feet of sea stars, sea cucumbers and possibly also small sea urchins. Some preliminary observations on the ecology and general biology of the species are provided. All previous records of G. tellei in the Canary Islands are briefly reviewed and at least 30 new sightings made between June 2005 and April 2024 are added.

We report here for the first time the occurrence of the diogenid hermit crab species Diogenes curvimanus from the Canary Islands, which has been recorded previously from Atlantic European waters and the Mediterranean Sea. The species had been placed under the synonymy of D. pugilator until recently, and is the sole representative of Diogenes known from the islands. The specimens studied were observed between 2019 and 2023, suggesting that these could have recently settled into local habitats and developed a population capable of reproducing.

Introduction: Sea urchin diseases have been documented in several locations worldwide, with reported occurrences of bacterial, protozoan, fungal, and algal infections. Objective: This study aimed to investigate pathogen agents in populations of Arbacia lixula and Paracentrotus lividus along the coast of Gran Canaria Island (Central-East Atlantic, Spain). Methods: Sampling was conducted at San Cristobal beach, on the Northeast side of the island, where sea urchins were manually collected from depths of 1-3 m during June, July, and October 2022. Swab samples were taken from the external and internal areas of the lesions and cultured on various media plates. Results: Eight different pathogen agents, including bacteria and fungi, were identified, with Vibrio alginolyticus being the most frequently observed bacteria in all diseased sea urchin samples. Additionally, ciliated protozoans were found within the tests, potentially acting as opportunistic parasites. Conclusions: This research provides a unique perspective on bald sea urchin disease by identifying a significant number of associated pathogens, including Candida, previously unreported in diseased organisms. Furthermore, the study highlights the presence of an inflammatory response in tissues with bacterial colonies, offering crucial insights into understanding this sea urchin disease.

The growth parameters of Lethrinus harak were studied in Zanzibar water from 308 samples collected between June 2019 to May 2020 at Unguja Ukuu and Mkokotoni landing sites. The annulus count indicated that the majority of fishes captured were of three and four years old and very few were five, six, and seven years of age with a mean length of 17.69 cm, 21.04 cm, 24.18 cm, 25.86 cm, and 28.15, respectively. The number of rings was counted on the whole otolith and the growth rings were revealed to be formed annually, with the opaque margins generated from December to February and the hyaline ones during the rest of the year. The growth parameters were estimated as L∞=34.22cm, K=0.25 year-1, and t0=0.00. The total mortality (Z) was estimated as 0.68 year-1 and natural mortality (M) was estimated using Pauly's equation, as 0.65 per year-1 and fishing mortality (F) was 0.03 year-1, which gives an exploitation rate (E) of 0.04 year-1. Although these values indicate the species to be underexploited, the absence of older individuals 15 years and smaller below three years might have affected our findings.

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.