Fish morphological and parasitological traits as ecological indicators of habitat quality in a Mediterranean coastal lagoon

Abstract

Coastal lagoons are key ‘transitional’ aquatic environments for biodiversity conservation. Ecological indicators are useful tools for the management of water resources in the European Union. Among different biological communities, fish are a very sensitive tool to assess environmental integrity. Indeed, their parasites can be used as complementary indicators of habitat quality. Yet there is still a deep lack of information on ecological assessment using fish (along with their parasites) for coastal lagoons, particularly for the Iberian Peninsula. The aim of the present study was to assess the use of fish morphology and their parasite communities as ecological indicators of anthropogenic impact within the Mar Menor coastal lagoon (SE Spain), a Mediterranean area of special conservation concern for European/Iberian biodiversity. Fish samples (black‐striped pipefish Syngnathus abaster and marbled goby Pomatoschistus marmoratus) were collected in August 2022 from the Littoral (high level of nutrient enrichment) and Barrier habitats. Physical status (both external and internal indices), asymmetry (level of developmental instability), parasite load, diversity and life‐cycle complexity were compared between habitat types. Body condition and mainly the health assessment index were better in the Barrier habitat. Except for pectoral fins in pipefish, the fluctuating asymmetry was statistically greater in the Littoral habitat (i.e. with eutrophication leading to poorer fish development). The parasite load was higher in the Littoral habitat for both host fish species. However, the diversity and life‐cycle complexity of parasite communities were statistically lower in the Barrier habitat (a structurally simpler environment) only for gobies. This study demonstrates an elevated potential for certain fish morphological and parasitological traits to be considered as good ecological indicators of environmental health. This could help environmental managers and policy makers to design effective monitoring programmes to detect impacts within valuable areas for conservation, such as the Mar Menor coastal lagoon.

Seasonal Effects on Health Status and Parasitological Traits of an Invasive Minnow in Iberian Waters

“…Morphological and parasitological examinations followed laboratory procedures welldescribed in Cruz et al [18] and Almeida et al [27], as well as references therein. On arrival at the laboratory, fish were stored in 50 L aquaria after a 30 min period of acclimatization.…”

“…Specifically, HAI consists of examining a variety of external/internal organs: skin, eyes, gills, alimentary tract, heart, liver, spleen, and gonads. Abnormalities, color, size, and condition are assessed for each organ, which is assigned a score ranging from 0 (healthy) to 30 (unhealthy) points (see Almeida et al [27] for the particular algorithm). Theoretically, the maximum value for HAI would be 240 (i.e., 30 points × 8 organs) per specimen.…”

“…During examinations to compute HAI, both ecto-and endo-parasites were also identified and counted per fish individual. In the present study, >30 fish specimens per site were examined (see sampling sizes above) for parasites, which is a sufficient number to achieve a good representation of infra-communities for this minnow species [18], as well as other fishes (see an example for pipefish and gobies from a Mediterranean coastal lagoon in Almeida et al [27]). Parasites were identified under dissecting (40×) and light (1000×) microscopes, using specific keys [30][31][32].…”

“…To explore temporal patterns, quantitative descriptors were used to properly analyze the variation in parasitological traits across seasons. Three parameters of parasite infracommunities were calculated for each fish individual (adapted from Bush et al [25]): 'Total Abundance' (TA, total number of parasite individuals detected from the examined organs), 'Diversity' (Shannon index H', calculated by using log 2 ) and a 'Life-cycle Complexity Index' (LCI, see a detailed explanation and formula in Almeida et al [27]). The number of different hosts ranged from one to three species for the parasite taxa found in the present study and consequently, the descriptor LCI (weighted by parasite abundances) also varied within this range.…”