Discarded catches in the main fishing areas of the Turkish coasts of the Aegean Sea were studied using data from commercial trawlers. The study area spans the Turkish coast of the Aegean Sea from Saros Bay (north) to Güllük Bay (south), and data were collected from trawl fishing grounds between April 2010 and 2012. Particular attention is paid to discard per unit effort (DPUE) and discard ratio. Generalized additive modelling (GAM) techniques with Tweedie family and log-link function were used to examine various predictor variables (duration, season, depth, longitude and latitude) on the DPUE of total catch. Discard ratio varied from 0.01 in winter at Çanakkale to 0.90 in summer at Güllük. Total discard ratio was calculated to be 0.33 for pooled data. The DPUE values ranged between 0.2 kg h–1 in autumn at Sığacık and 45.5 kg h–1 in spring at Güllük, with a mean value of 7.6±5.7 kg h–1. Modelling DPUE values in relation to season vs coordinates revealed spatio-temporal differences. The relationship between the dependent variable (DPUE) and the independent variable (depth) showed fluctuations, but haul duration displayed a decreasing trend in the modelling. It was determined that a considerable amount of trawl discards was obtained in the Aegean Sea. The results of this paper should be considered to create a regional discard policy and management plan in the eastern Mediterranean.

Taxonomic identification of alien bivalve species in the Mediterranean Sea can be challenging because of high morphological variability and the occurrence of cryptic species complexes, as in the case of pearl oysters. While the presence of the Lessepsian species Pinctada radiata is well-established in the eastern Mediterranean Sea, the presence of P. fucata was recently suggested based on morphological data. In this study we performed an integrative assessment based on morphological and genetic data on pearl oysters collected across the Mediterranean Basin. Molecular species delimitation and phylogenetic analyses allowed a straightforward taxonomic assignment of all collected specimens to P. radiata. These specimens show the entire suite of morphological character states considered diagnostic of either P. fucata or P. radiata by previous studies. This finding clearly demonstrates that these morphological characters have no taxonomic value, and their variability observed in specimens from the Mediterranean Sea represents (part of) the intraspecific variability of P. radiata. While no evidence has been found for the presence of P. fucata, the earlier occurrences of P. radiata from the eastern and southern Mediterranean Sea are complemented with verified occurrence in the western and northern regions, demonstrating a further spreading of this non-native species throughout the Mediterranean Sea. This study clarifies the taxonomic identification and geographical distribution of pearl oysters in the Mediterranean Sea and substantiates the importance of molecular identification of alien bivalves characterized by extensive variation in shell characters.

The hypothesis of this study was that significant variations in the growth rates of Goniopsis cruentata are related to intersexual and age-related characteristics, particularly in areas identified as secondary sexual (pleon, carapace and chelipeds). From February 2019 to January 2020, a total of 713 individuals were captured, 378 males and 335 females, with a carapace width ranging from 0.42 to 6.59 cm. Males and females showed negative allometry (β0<1) for all linear morphometric relationships, with an ontogenetic difference (p=0.0001) for all comparisons. In geometric morphometry, the dorsal view showed a significant difference in sexual comparisons (p=0.0001), in which males were wider in the posterior region than females. Furthermore, there was a significant difference in the abdominal region between young and adult females (p=0.0001), with the young ones being triangular and the adults oval, a characteristic brachyuran behaviour. We observed morphological separation in cheliped shape in sexual comparison (F×M) and laterality (R×L) (p=0.0001), with no ontogenetic variations (A×J). Goniopsis cruentata showed a noteworthy ontogenetic and sexual dimorphism. In addition, the discovery of cheliped variation was recorded for arboreal species that do not show a high degree of heterochely. Understanding these ontogenetic variations is crucial for effective conservation strategies because it allows specific life stages and their corresponding needs to be identified.

Marine protected areas (MPAs) have been used for biodiversity conservation for decades. However, critics argue that evidence of their economic benefits is weak, particularly with regard to fisheries. This continued opposition to MPAs for fisheries slows progress towards conservation targets and undermines the economic and ecological sustainability of the oceans. This paper provides 48 examples of fishery-related and 31 of tourism-related economic benefits in 25 and 24 countries, respectively. There was no evidence of net costs of MPAs to fisheries anywhere. Fishery benefits included increased fish stocks, catch volumes, catch per unit effort, fecundity and larval export, and larger fish and lobsters. Well-designed and enforced MPAs provide sustainable benefits for fishing communities and even sub-optimally designed MPAs can provide economic advantages. MPAs represent one of the best strategies for maintaining the sustainable exploitation of marine resources.

Identifying cryptic species is pivotal for understanding marine biodiversity and optimizing strategies for its conservation. A robust understanding of poriferan diversity is a complex endeavour. It has also been extremely hampered by the high phenotypic plasticity and the limited number of diagnostic characters. Mycale (Carmia) cecilia has different body colours, even among individuals living together. We tested whether the colour variation could be due to polymorphism, phenotypic plasticity or cryptic speciation. Phylogenetic reconstructions of nuclear and mitochondrial loci were congruent. Individuals of different body colour did not cluster together and had high levels of genetic divergence. Furthermore, the green morphotype clustered in almost all reconstructions with Mycale (C.) phyllophila, as both showed higher gene similarity at the transcriptomic level (public transcriptome). Morphologically, the green individuals consistently showed discrepancies from the red ones. These results suggest that all individuals with the same body colour, either red or green, correspond to the same species, while individuals with different body colours probably belong to different species. These results reveal high levels of morphologic and genetic diversity, which could have important implications for what is known as M. (C.) cecilia and the Mycalidae systematics.

Our general purpose is to support the use of known-biomass production models (KBPMs), illustrating their usefulness by addressing the evolution of surplus production (SP) over time and the factors affecting it (e.g. environment). We also demonstrate the utility of KBPMs for multispecies management objectives or for estimating maximum sustainable yield reference points without a stock recruitment function, among other worthwhile applications. To do so, we present different uses of KBPMs, illustrating their application on demersal species in the International Council for the Exploration of the Sea (ICES) area, specifically for megrim, white anglerfish and European hake stocks. The proposed analytical approach involved fitting single-species and multispecies KBPMs, conducting retrospective analyses and assessing the effects of environmental variability on SP. The findings show that, in general, stock SP increased after a decline in biomass and SP, except for white anglerfish in the southern area. Megrim stocks are the least productive, while hake and northern anglerfish are the most productive. Retrospective analysis revealed SP shifts in northern hake stock for reasons other than biomass variability. Hence, the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation (AMO), two key climate variability modes in the North Atlantic, were tested for their links to SP, revealing a positive connection between SP and AMO, although further research is necessary. Beyond the specific results of our particular KBPM application, our main conclusion is that KBPMs can serve as a tool complementary to more complex assessment models for resolving unaddressed issues and crosschecking available assessment results.

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.