The stock-recruitment (S-R) relationship describes how the amount of spawning stock biomass relates to the number of new individuals entering the harvestable population. This relationship is fundamental for designing sustainable harvest strategies and stock recovery plans for depleted fisheries, such as Mexican abalone. Due to their slow growth, external fertilisation, and planktonic larvae, these species are particularly vulnerable to irreversible decline under fishing pressure and environmental change, or their possible combined effect. This study evaluated five S-R models to determine which best describes the S-R relationship of pink abalone (Haliotis corrugata) in the northern Mexican Pacific. Model comparison favoured the Saila-Lorda formulation, which provided the best description of the S-R relationship in this dataset. Lagged regression analyses indicated that sea surface temperature (SST) was a significant predictor of recruitment variability (p < 0.01), with the strongest association occurring at a three-year lag. Together, these results suggest that environmentally mediated processes can modify the effective S-R response through time, consistent with temporally driven depensation under unfavourable thermal conditions. Integrating temperature signals into assessment and management frameworks may therefore improve the design of adaptive harvest strategies and support recovery of pink abalone under ongoing climate variability.
The intertidal gastropod Umbonium vestiarium (Linnaeus, 1758) shows remarkable shell colour variation throughout the Indo-Pacific region, but no detailed quantitative study had previously examined this polymorphism in the ecologically diverse Sundarban Biosphere Reserve (SBR), West Bengal, India. This study provides the first comprehensive assessment of shell colour polymorphism in the SBR using multiple analytical approaches across six intertidal islands representing different environmental conditions of the Indian Sundarbans. A total of 4033 individuals were collected from 60 quadrats (25 & times; 25 cm = 1/16 sq. metre), and eleven distinct colour morphs (P1-P11) were identified through a standardised 25-character binary matrix, which resolved three colour-pattern-based morph groups by UPGMA cluster analysis. Morphometric analysis of 330 specimens revealed significant shape variation among morphs, and discriminant analysis separated all eleven colour-defined morphs in shape space. However, clustering based on shape alone did not match colour-based groupings, showing shell shape and colour vary along decoupled axes. Uneven morph distribution across islands suggests environmental influence, consistent with environmentally structured divergence in the Sundarbans, although without proof. Morphs P4 and P9 are potential conservation priorities, and this frequency data offers a baseline for future biodiversity monitoring.
Marine bivalves rely on physiological and structural mechanisms to cope with environmental variability, yet shell formation responses to thermal fluctuations remain poorly understood. This study evaluated shell development and biomineralization-related responses in juvenile lion's paw scallops, Nodipecten subnodosus, derived from Laguna Ojo de Liebre (LOL) and Bah & iacute;a de Los & Aacute;ngeles (BA). Juveniles were exposed for 15 days to constant temperature, regular thermal oscillations, or chaotic thermal oscillations. Shell responses were assessed using shell index (SI), expression of a putative mucin-related transcript, and qualitative scanning electron microscopy. Tank-level analysis detected a significant overall effect of source population on SI, whereas neither thermal regime nor its interaction with source population was statistically significant. A model-estimated contrast showed that BA scallops had a higher SI than LOL scallops under the chaotic regime; however, this difference does not demonstrate that chaotic oscillations directly reduced shell deposition. Expression of the putative mucin-related transcript did not differ significantly in the comparisons evaluated. Apparent alterations in outer and inner shell structures morphologically consistent with calcitic and aragonitic organisation were observed under both oscillatory regimes. Overall, SI, transcript expression, and shell microstructure showed non-parallel responses, indicating that these endpoints capture complementary aspects of shell formation under thermal variability.
Understanding the composition of omnivores' diet in their habitats is difficult, especially in endangered taxa. Faecal DNA metabarcoding could be one of non-invasive methods that may help resolve this problem. The critically endangered Japanese land snail Euhadra murayamai Habe, has only been recorded from a single vertical limestone cliff, where direct examination of its feeding ecology is physically difficult. We obtained sufficient sequencing reads of a partial chloroplast trnL intron region from faeces of 10 and 4 individuals sampled in July and October, respectively. The operational taxonomic unit (OTU) compositions detected from these samples were similar between these months. In total, 14 of 45 OTUs were assigned at or below the order level using an automated pipeline. Subsequent manual BLAST searches, combined with verification against plant species recorded during field surveys, enabled assignment to 10 different species across eight orders. These results support that E. murayamai eats plant-derived materials from diverse plant taxa in its habitat. Our findings highlight the methodological potential of faecal DNA analysis for investigating the ecological resources of terrestrial molluscs.
In scientific investigations involving molluscs, various anaesthetics are used, with magnesium chloride proving itself to be effective. In this study, the effect of different concentrations of magnesium chloride solutions (4%, 7% and 10% w/v) was evaluated in juvenile and adult Pomacea diffusa, measuring relaxation, anaesthesia and recovery times and analysing the influence of the origin of the gastropods on these parameters. Specimens were collected from two different localities (Jauary and Centen & aacute;rio) in Itacoatiara, Amazonas, Brazil. Increasing magnesium chloride concentration reduced relaxation and anaesthesia times in juveniles and adults. Relaxation times (4%, 7%, 10%) were 16.91 +/- 3.65, 14.48 +/- 2.50, and 12.40 +/- 2.73 min in juveniles, and 30.12 +/- 5.39, 29.44 +/- 7.70, and 20.90 +/- 7.49 min in adults. Anaesthesia times were 22.21 +/- 3.85, 18.06 +/- 2.72, and 16.12 +/- 2.58 min in juveniles, and 37.25 +/- 5.12, 36.54 +/- 7.59, and 25.80 +/- 7.94 min in adults. Relaxation, anaesthesia, and recovery times differed significantly between juveniles and adults, although the different populations responded similarly. Thus, anaesthetic efficacy in P. diffusa was influenced by concentration and sexual maturity, with higher concentrations increasing efficacy and adults showing longer recovery times.
