Alexandre Alonso-Fernández

The use of Histological Techniques to Study the Reproductive Biology of the Hermaphroditic Mediterranean Fishes Coris julis, Serranus scriba, and Diplodus annularis

Abstract The usefulness and importance of histological techniques in reproductive studies have been widely discussed for gonochoristic fish species. In the case of hermaphroditic fishes, histology is a particularly important tool for the proper identification of sexual pattern (i.e., sequential, simultaneous, or nonfunctional hermaphroditism). We used a histological approach to describe hermaphroditism, dynamics of follicle development, and spawning patterns in three species from the northwestern Mediterranean Sea (Balearic Islands, Spain): the Mediterranean rainbow wrasse Coris julis (sequential hermaphrodite), painted comber Serranus scriba (simultaneous hermaphrodite), and annular sea bream Diplodus annularis (nonfunctional hermaphrodite). Development of secondary growth follicles was asynchronous in all three species, and similar peaks in spawning activity occurred between May and July. However, notable differences in sexual cycle and egg production were found. For the painted comber, hydrated follicles were present in ovarian tissue almost every day during the peak of the spawning season, suggesting daily spawning and increasing the chances of autofertilization unless a mechanism to avoid this action is present in this species. Intersexual Mediterranean rainbow wrasses were identified, and the size and age at sex change were estimated to be 132 mm total length and 4 years, respectively. Previous investigators have concluded that the annular sea bream is a protandric hermaphrodite, but our results indicate nonfunctional hermaphroditism. These three species are of little commercial interest and are considered to be bycatch by the artisanal fleet, but they are vulnerable to the impacts of some recreational angling activities. Currently, no specific management plan has been developed for these species. We address the importance of describing sexual pattern and its implications for future conservation efforts.

Demographic Variation between Colour Patterns in a Temperate Protogynous Hermaphrodite, the Ballan Wrasse Labrus bergylta

Fish populations are often treated as homogeneous units in typical fishery management, thereby tacitly ignoring potential intraspecific variation which can lead to imprecise management rules. However, intraspecific variation in life-history traits is widespread and related to a variety of factors. We investigated the comparative age-based demography of the two main colour patterns of Labrus bergylta (plain and spotted, which coexist in sympatry), a commercially valuable resource in the NE Atlantic. Individuals were aged based on otolith readings after validating the annual periodicity of annuli deposition. The relationships between the otolith weight and fish age and between otolith length and fish length were strong but differed between colour patterns. The fit of the growth models to the age and length data resulted in divergent growth curves between colour morphotypes and between sexes. Males and spotted individuals attained larger mean asymptotic sizes (Linf) than females and plain individuals, respectively, but converged to them more slowly (smaller k). Estimates of mortality based on catch curves from two independent datasets provided a global total mortality (Z) of 0.35 yr–1, although Z was larger in plain and female individuals. Overall, the results of this research have direct implications for management of L. bergylta and, as a precautionary measure, we recommend considering both colour patterns as two different management units.

Intraspecific variability in reproductive patterns in the temperate hermaphrodite fish, Labrus bergylta

For many fish populations reproductive patterns remain unknown, which often results in inadequate management strategies. Timing and intraspecific variability in the main reproductive traits of ballan wrasse (Labrus bergylta) were investigated based on microscopic analysis of gonads sampled from NW Spain in 2009–2012. This species displays two main body colour patterns, plain and spotted, which coexist in sympatry. Females spawned from January to April whereas spawning capable males were present almost year-round. Length at 50% maturity did not differ between colour patterns and was above the minimum catch size. Plain individuals attained the length and age at 50% sex change earlier than spotted individuals, which might be explained by differences in growth patterns, mortality rates or by an evolutionary genetic divergence between populations. Individuals with gonads infected by encysted trematode metacercariae were associated with an earlier timing of sex change, which represents one of the few examples of a possible parasitic influence on the sex allocation of its host. Our findings provide a framework for scientific-based management of this hermaphrodite fish.

Geographic range expansion of Ephippion guttifer (Tetraodontidae) in the north-eastern Atlantic

The first record of the prickly puffer Ephippion guttifer (Tetraodontidae) from Galician waters (north-west Spain) is reported based on a male specimen of 570 mm total length (LT ) caught in the Ría de Vigo. Morphometric, meristic and DNA barcode data confirmed the identification. Histological examination of reproductive tissue was carried out in this species for the first time, showing a mature male in an actively spawning phase. A historical revision invalidates a previous record and establishes this as the northernmost confirmed capture ever reported in the north-eastern Atlantic Ocean.

New records of two southern fishes found in northern waters of the Iberian Peninsula

The first records of the spearfish remora, Remora brachyptera (Lowe, 1839) (Actinopterygii: Echeneidae), and the white grouper, Epinephelus aeneus (Geoffroy Saint-Hilaire, 1817) (Actinopterygii: Serranidae), from northern Spanish waters are reported. Both findings are, respectively, the second and the first northernmost reports, for both fish species, in the eastern Atlantic. Morphometric and meristic parameters, along with DNA barcoding, confirmed the identification of the remora specimen. Results of the histological examination of the gonads of R. brachyptera are also reported, showing a mature male at the developing maturity phase. The grouper specimen was identified taking into account its characteristic coloration based on a photograph.