Open research questions in Ichthyology and Marine Biology

What the literature leaves open

• The Eastern Tropical Pacific (ETP) Spotted Eagle Ray, Aetobatus laticeps Gill, 1865, is an understudied species with limited information on its ecology and conservation status.

  Phylogeography and population genetics of the white spotted eagle ray, Aetobatus laticeps Gill, 1865, in the Eastern Tropical Pacific · 2026 · DOI

• These findings extend the known southeastern Mediterranean distribution of the Honeycomb Whipray, highlight the Gaza Strip as an under-reported hotspot for rare elasmobranch records, and emphasize the urgent need for fisheries monitoring, taxonomic verification, bycatch mitigation, and conservation measures for threatened batoids in Palestinian waters.

  Rare Records of the Exotic and Endangered Honeycomb Whipray (Himantura uarnak Forsskål, 1775) in the Mediterranean Waters off the Gaza Strip, Palestine · 2026 · DOI

• Although this study provides evidence of overlap with mesopelagic prey resources, several limitations preclude a more definitive interpretation of basking shark foraging ecology. Concurrent hydroacoustic data on scattering layer structure and composition were not available during tag deployments and were therefore inferred from published observations. Previous work has attempted basin-scale alignment of predator dive data with modeled DSL depth [31], but model- derived estimates of the primary DSL vary substantially across regions and seasons and do not provide any inference on secondary DSLs. Accordingly, our inferences rely on clustering of vertical habitat use, regional descriptions of scattering layer structure, and in situ proxies such as isolume depth and bioluminescence detection. Future research integrating multi-sensor biologgers, animal-borne cameras, and surface or in situ acoustic surveys (e.g., [81,82]) would substan- tially improve understanding of prey community composition and distribution and illuminate predator–prey interactions at depth.

  Basking sharks overlap with primary and secondary deep scattering layers during overwintering migration in the Northwest Atlantic Ocean · 2026 · DOI

• The basic question of whether or not imperiled species should ever be collected from the wild, particularly during a time of rapid climate change, habitat alteration and degradation, overexploitation, and other anthropogenic effects (Cafaro, 2015), regardless of whether it is for profit or not, is an ongoing and healthy debate that is beyond the scope of this paper.

  Reconciling conservation and management objectives with the international aquarium trade of the globally critically endangered Sand Tiger Shark · 2026 · DOI

• The tiering framework relies on density and persistence measures to identify fish nurseries but lacks explicit guidance on minimum temporal resolution and sampling intensity required for reliably distinguishing true nursery areas from transient juvenile aggregations across different habitat types and geographic scales.

  A decision tree to guide precautionary and adaptive tiering in marine nursery identification and management · 2026 · DOI

• Governance and implementation mechanisms for transitioning from single-sector to ecosystem-based management of nursery areas require explicit evaluation within the tiering framework. The paper cites socioeconomic factors underpinning marine protected area effectiveness but does not specify how knowledge co-production and collaborative governance should modify precautionary tiering decisions.

  A decision tree to guide precautionary and adaptive tiering in marine nursery identification and management · 2026 · DOI

• The framework does not address how citizen science monitoring and community-based observational data can be integrated into marine nursery identification to overcome distributional monitoring gaps in data-limited regions. Specific validation protocols are needed to assess accuracy thresholds for species identification in citizen science fish nursery surveys.

  A decision tree to guide precautionary and adaptive tiering in marine nursery identification and management · 2026 · DOI

• Anthropogenic disturbance effects on nursery function in estuarine and coastal areas lack standardized quantitative assessment protocols within the tiering framework. Research must specify measurable thresholds for evaluating how trawl fishing pressure, habitat modification, and industrial activity degrade nursery effectiveness across different tiering levels.

  A decision tree to guide precautionary and adaptive tiering in marine nursery identification and management · 2026 · DOI

• The paper identifies that linking juvenile habitat utilization to population fitness requires integration of source-sink population dynamics models with spatial nursery area mapping, but the specific quantitative methods for translating nursery identification outputs into population-level sustainability metrics for data-limited fisheries remain unspecified.

  A decision tree to guide precautionary and adaptive tiering in marine nursery identification and management · 2026 · DOI

• The decision tree framework for marine nursery identification lacks empirical validation across different ecoregions and fish life histories. Specific testing is needed to determine how precautionary and adaptive tiering thresholds should be adjusted for species with different ontogenetic habitat shifts, particularly for elasmobranchs and demersal fish with poorly documented juvenile recruitment dynamics.

  A decision tree to guide precautionary and adaptive tiering in marine nursery identification and management · 2026 · DOI

• Capacity-building programs for fisheries officers and traders in elasmobranch species identification have not been evaluated for effectiveness at TPI Ujungbatu; sustained training programs targeting identification accuracy and enforcement of Regulation Number 61/PER-MENKP/2018 must be developed and tested to improve compliance with national and international regulations.

  Species Diversity, Conservation Status, and Policy Gaps of Landed Elasmobranchs at Ujungbatu Fish Landing Site, Jepara in Support of SDG 14 (Life Below Water) · 2026 · DOI

• Mandatory reporting and monitoring systems do not exist across all major elasmobranch landing sites in Indonesia; implementation of standardized landing site monitoring protocols at TPI Ujungbatu and comparable sites is required to generate consistent baseline data for tracking population trends in Critically Endangered taxa.

  Species Diversity, Conservation Status, and Policy Gaps of Landed Elasmobranchs at Ujungbatu Fish Landing Site, Jepara in Support of SDG 14 (Life Below Water) · 2026 · DOI

• A regulatory gap exists where 57.14% of landed elasmobranchs (n=64 specimens) belong to unregulated species despite 78.57% of total catch comprising IUCN-threatened species; Dasyatidae species classified as Endangered or Vulnerable must be evaluated for inclusion in CITES Appendices to close loopholes enabling unmonitored exploitation.

  Species Diversity, Conservation Status, and Policy Gaps of Landed Elasmobranchs at Ujungbatu Fish Landing Site, Jepara in Support of SDG 14 (Life Below Water) · 2026 · DOI

• Molecular species identification using DNA barcoding has not been applied to resolve genus-level taxonomic ambiguities within Carcharhinus and Pateobatis complexes at Ujungbatu; implementing DNA barcoding protocols is essential to improve landing data accuracy and prevent misidentification that masks actual catch composition of threatened species.

  Species Diversity, Conservation Status, and Policy Gaps of Landed Elasmobranchs at Ujungbatu Fish Landing Site, Jepara in Support of SDG 14 (Life Below Water) · 2026 · DOI

• Species-specific catch quotas for elasmobranchs at Ujungbatu and other major landing sites require foundational population assessments that currently do not exist; these assessments must be conducted for Critically Endangered species like Rhynchobatus australiae (30.36% of observed landings) to establish scientifically defensible catch limits.

  Species Diversity, Conservation Status, and Policy Gaps of Landed Elasmobranchs at Ujungbatu Fish Landing Site, Jepara in Support of SDG 14 (Life Below Water) · 2026 · DOI

• Non-Detriment Findings (NDF) mechanisms for CITES-listed elasmobranch species are absent in Indonesia; robust NDF processes must be developed and synchronized with landing data at major fishing sites to scientifically verify that international trade of threatened species, particularly Rhinopristiformes and wedgefish, does not deplete wild populations.

  Species Diversity, Conservation Status, and Policy Gaps of Landed Elasmobranchs at Ujungbatu Fish Landing Site, Jepara in Support of SDG 14 (Life Below Water) · 2026 · DOI

• Bait attraction in BRUVS may bias detection toward more inquisitive or food-motivated individuals, potentially inflating juvenile abundance estimates rather than reflecting true differences in abundance.

  Spatiotemporal patterns and habitat associations of blacktip reef shark in a shallow tropical bay · 2026 · DOI

• The small body size of neonates and young-of-the-year juveniles (< 90 cm) limited reliable identification from drone footage, representing a detection gap that prevented comprehensive juvenile assessment.

  Spatiotemporal patterns and habitat associations of blacktip reef shark in a shallow tropical bay · 2026 · DOI

• Further studies combining existing data with molecular and morphological data, ideally also including DNA sequence information of type material, from more Southern Hemisphere specimens are necessary to resolve the taxonomic conundrum.

  First record of an ilyophine eel (Anguilliformes, Synaphobranchidae) from the Southern Ocean · 2026 · DOI

• Conflicting records exist for Raja radula and Raja asterias regarding their presence and abundance in the Adriatic, with the checklist providing outdated last records (1984 and 1994-1998) while recent studies suggest these species are still present and common.

  Comment on Balàka et al. Updated Checklist of Chondrichthyan Species in Croatia (Central Mediterranean Sea). Biology 2023, 12, 952 · 2024 · DOI

• Species identification status in the Adriatic remains confused and contradictory across sources; e.g., Chimaera monstrosa is reported as rare (last record 1996) by the checklist authors but abundant (36.4% of stations) by other researchers in deep waters.

  Comment on Balàka et al. Updated Checklist of Chondrichthyan Species in Croatia (Central Mediterranean Sea). Biology 2023, 12, 952 · 2024 · DOI

• White sharks (Carcharodon carcharias), the most visible in popular culture, remain vulnerable (VU, IUCN Red List) and understudied, although population recovery is having a measure of success in regions like the Eastern Pacific and the Northern Atlantic of the United States.

  Jumping the Shark: White Shark Representations in Great White Serial Killer Lives—The Fear and the (Pseudo-)Science · 2021 · DOI

• The present paper describes the identification of a very rarely recorded and poorly studied copepod of the family Philichthyidae – Philichthys xiphiae Steenstrup, 1862 – in a dead swordfish found on a sea beach in Dźwirzyno (Poland) in 2016.

  <i>Philichthys xiphiae</i> (Copepoda; Philichthyidae) – an interesting cranium parasite of the swordfish <i>Xiphias gladius</i> collected from the Baltic Sea · 2021 · DOI

• Dispersal influences many fundamental processes, however, direct measures of dispersal are scarce for most taxa, limiting our ability to evaluate ecological theory at broad scales.

  From wings to tails: the aspect ratio of propulsive surfaces as a general proxy for vertebrate dispersal potential · 2026 · DOI

• The Cretaceous-Paleogene (K-Pg) extinction reshaped Earth's biodiversity, yet its impact on marine fishes remains debated due to gaps in the Paleocene record.

  Rise of modern marine fishes captured in an early Paleocene Lagerstätte · 2026 · DOI

Most-cited papers in Ichthyology and Marine Biology

• Ecological erosion and expanding extinction risk of sharks and rays · Science · 2024 · 66 citations
• The BRUVs workshop – An Australia-wide synthesis of baited remote underwater video data to answer broad-scale ecological questions about fish, sharks and rays · Marine Policy · 2021 · 44 citations
• The Salas y Gómez and Nazca ridges: A review of the importance, opportunities and challenges for protecting a global diversity hotspot on the high seas · Marine Policy · 2021 · 34 citations
• Fine‐scale oceanographic drivers of reef manta ray (<i>Mobula alfredi</i>) visitation patterns at a feeding aggregation site · Ecology and Evolution · 2021 · 30 citations
• Local ecological knowledge of fisheries charts decline of sharks in data-poor regions · Marine Policy · 2021 · 19 citations
• Preliminary Assessment of Invasive Lionfish <i>Pterois miles</i> Using Underwater Visual Census Method in the Northeastern Mediterranean · Croatian Journal of Fisheries · 2022 · 14 citations
• New records of sharks (Elasmobranchii) from the Andaman and Nicobar Archipelago in India with notes on current checklists · Biodiversity Data Journal · 2018 · 13 citations
• The Kraken: when myth encounters science · História Ciências Saúde-Manguinhos · 2014 · 11 citations
• Toward an atlas of Salish Sea biodiversity: the flora and fauna of Galiano Island, British Columbia, Canada. Part I. Marine zoology · Biodiversity Data Journal · 2022 · 7 citations
• Some Population Parameters of Picked Dogfish (Squalus acanthias L. 1758) Incidentally Captured in Commercial Fisheries in Southern Black Sea Shores and a First Record of Angular Roughshark (Oxynotus centrina, L. 1758) for Black Sea · Marine Science and Technology Bulletin · 2023 · 7 citations

Most recent work

• Spatiotemporal patterns and habitat associations of blacktip reef shark in a shallow tropical bay · Environmental Biology of Fishes · 2026
• Assessing awareness and perceptions of shark fishing regulations for improved fisheries management · Oryx · 2026
• Partial sympatry of two interspersed Uroteuthis edulis (Loliginidae) clades reveals cryptic stock structure in the southern Taiwan Strait · Fisheries Research · 2026
• The Red Sea's largest coastal lagoon is a reproductive site for endangered whiprays and guitarfish · Endangered Species Research · 2026
• Rise of modern marine fishes captured in an early Paleocene Lagerstätte · Science Advances · 2026
• A complex pigmentation disorder reveals energetic and ecological costs of coloration in a deep‐sea sharpnose sevengill shark · Journal of Fish Biology · 2026
• Distribution and ecology of the four <scp> <i>Macrourus</i> </scp> species by‐caught in the longline fishery at South Georgia, Southern Ocean · Journal of Fish Biology · 2026
• First record of an ilyophine eel (Anguilliformes, Synaphobranchidae) from the Southern Ocean · Antarctic Science · 2026
• Species Diversity, Conservation Status, and Policy Gaps of Landed Elasmobranchs at Ujungbatu Fish Landing Site, Jepara in Support of SDG 14 (Life Below Water) · Jurnal Penelitian Pendidikan IPA · 2026
• Whole-genome sequencing suggests taxonomic inflation in the Careproctus snailfishes (Liparidae) of the northeast Atlantic–Arctic region · Polar Biology · 2026

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