Avances en acuariología y conservación de especies marinas

Abstract

Rapid population growth since the mid-20th century has resulted in increased pressure on ecosystems. In recent decades, an increasing deterioration of the environment has been observed, mainly due to anthropogenic factors. Conservation strategies for endangered species need multidisciplinary approaches and require a combination of in situ and ex situ actions, selected considering the specific needs of each species and the threats it faces. The present work is about the conservation of the pen shell (Pinna nobilis Linnaeus, 1758) and is divided into three chapters, the first of which is an in situ study on the diagnosis of the Mar Menor population from its entry into the lagoon to the present time. The next two are ex situ work in a closed system focusing on maintenance and breeding protocols for the species. The populations of the pen shell (Pinna nobilis) have declined progressively in recent decades because of anthropogenic activities. The species' regression increased exponentially since 2016, when a mass mortality event triggered by the parasite Haplosporidium pinnae occurred, although other pathogens may have been involved. The epidemic spread throughout the Mediterranean Sea, relegating their populations to coastal lagoons or estuaries with salinities outside the 36.5-39.7 psu range. The Mar Menor is one of the two locations with these characteristics on the Spanish coast. In the early 1980s, P. nobilis appeared in the Mar Menor lagoon and colonised it rapidly. However, the dispersion of the pen shell in the lagoon was interrupted in 2016 (in parallel to the mass mortality taking place in the Mediterranean) when the population was decimated by a crisis that affected more than 99% of the specimens as a consequence of eutrophication and anoxia events, which became critical in 2016, 2019 and 2021. In the first chapter, we estimated the variations in the potential distribution and density of P. nobilis in the different periods from the colonisation of the lagoon to the present, using two-stage species distribution models (presence/absence estimation and density modelling). The main environmental variables that determined the dispersion and colonisation of the Mar Menor by the bivalve in stages prior to 2016 have been studied, as well as the variables that have modified its distribution in the lagoon after the successive eutrophication crises. The second chapter deals with the establishment of ex situ maintenance protocols for Pinna nobilis. Appropriate recirculation systems have been designed for the maintenance of the species, the appropriate technology has been selected to reproduce the environmental conditions and their annual variations in controlled laboratory environments, and advances have been made in the development of suitable diets and pathogen control therapies to ensure their viability over time in facilities outside their natural environment. The third chapter delves into one of the key objectives to prevent the decline of Pinna nobilis and its extinction, progress in the development of ex situ reproduction protocols considering in situ and ex situ maturation procedures, as well as the fine-tuning of the methodology to ensure larval survival. The viability of the Mar Menor population depends on management actions designed both for the species and to improve the environmental status of the lagoon.