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The present study aims to investigate the reproductive biology of the small pelagic Sardinella aurita Valenciennes, 1847 in the Canary Islands, to enable its reliable assessment and advise on appropriate management measures for a fishing resource showing a declining trend in landings. Reproductive biology and sexual patterns of round sardinella were examined from monthly random samples of commercial catches landed by the artisanal purse-seine fleet. The landings' length frequencies, ranging between 9–32 cm (based on the total lengths, TL), were recorded from 2013–2019. The overall mean value of TL was 20.9 cm, with annual mean values between 20–22 cm, except in 2016 (TL = 19 cm). The overall sex ratio M:F was 1:0.92, with males significantly predominant. Sex ratios fluctuated as a function of size and month: females were more abundant in the larger length classes, as well as before and after spawning, whereas males were more abundant in the smaller length classes and during spawning. Based on gonad maturity stages and gonadosomatic index, round sardinella spawns during almost all the year, with a peak in January–February and a resting period during October–November. The length at first maturity was estimated at TL of 18.2 cm, notably smaller than the value obtained for the NW African coastal waters where the demographic structure in round sardinellas' landings is totally different., SI

This is the first study addressing validation of the early growth stages (including the first increment) in the beaks of juvenile cuttlefishes. The age validation in juveniles of Sepia officinalis was performed by comparison of the number of increments observed in the rostrum surface of lower jaws with their true age. A total of 159 individuals were reared at 18 ºC and 21 ºC, with ages up to 31 days from hatching. The number of growth increments in the beak was counted and contrasted with the days of life after hatching, validating the hypothesis of one increment of growth corresponding to one day of life. The mean coefficient of variation between readings (measuring precision) was 2.95 ± 5.98%. The growth of the reading area (rostrum surface) and the periodicity of increment deposition showed no difference between the two culture temperatures and therefore daily deposition was confirmed at these temperatures., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Guerra-Marrero was supported by a PhD-fellowship (PIFULPGC-2017-CIENCIAS-2) from the University of Las Palmas de Gran Canaria.

Los datos puros del artículo pueden consultarse en el siguiente enlace: https://doi.org/10.5281/zenodo.7351679., Squid play a major role in the Southern Ocean food web. However, their age and growth remain poorly studied. Here, using upper and lower beaks of Moroteuthopsis longimana collected from the diet of Dissostichus mawsoni from Pacific and Atlantic sectors of the Southern Ocean, we studied: (1) Feasibility of using beaks collected from predators’ stomachs to study the age of Southern Ocean oceanic squid; and (2) Age estimation and growth patterns of M. longimana. The rostrum sagittal section (RSS) of both beaks had micro-increments, with the lower beak being the best to observe and count a readable sequence of increments to estimate the age. Assuming a daily deposition of increments, our results suggest that M. longimana can live up to 820 days and may hatch throughout the year. Studied individuals presented a consistent growth rate from hatching to death but with, at least, one period of faster growth. A novel pattern of regular cycles, composed of 7–10 lighter increments followed by a darker one, was found in the medium-anterior region of the RSS. Differences were found in the growth rate and size reached at the same age between individuals from the Pacific and Atlantic sectors, which might be related with different environmental conditions between both capture sites. This study shows that lower beaks from predators’ stomachs can be used to study the age of Southern Ocean squids and that M. longimana hatches in all seasons, being available year round to predators that feed of this species., Open access funding provided by FCT|FCCN (b-on). This work was supported by the strategic program of Marine and Environmental Sciences Centre (MARE), financed by the FCT (UIDB/704292/2020). JPQ was supported by a FCT/MCTES through national funds (PIDDAC) and Portuguese Polar Program (PROPOLAR) and by FCT PhD scholarship co-financed by FSE (SFRH/BD/144320/2019).

The giant squid Architeuthis dux Steenstrup, 1857 is one of the largest and most enigmatic marine species. Its age estimation remains controversial with many estimates of maximum age ranging from 1 to 14 yrs. Successful results regarding the study of aging in cephalopod beaks for some octopod and oegopsid squids support using these structures for age estimation. We analyzed the beaks of 10 individuals, caught between 1995 and 2006, with reconstructed dorsal mantle lengths (DMLs) between 823 and 1418 mm. The beaks were measured and weighed, and their microstructure was analyzed in three ways: (1) in the rostrum area [rostrum sagittal sections (RSS)] for both upper and lower jaws, and the (2) inner lateral wall surfaces (LWS) and (3) inner crest surfaces (CS) for upper jaws. A constant sequence of increments was observed along the RSS, indicating that the use of lower jaws is more feasible due to the higher erosion and tighter packing of increments of upper jaws. The statolith of one individual was analyzed, resulting in 520 increments (579 increments from RSS of its lower jaw). Assuming daily deposition, the age estimations in RSS between 411 and 674 d suggest rapid growth of A. dux, averaging 1.97 mm DML d−1 (SD 0.45). When maximum ages were estimated by applying these results to the largest measured specimens in the literature (e.g., 2400 mm DML), an age of approximately 3 yrs was obtained. Analysis over a greater size range of individuals would allow more accurate age estimations of this emblematic squid., Sí

Global abundances and commercial fisheries of cephalopods have increased over recent decades, creating a need for effective fishery management. This management is often focused on the ability to ascertain the age structure of key populations. There are several main techniques for age and growth rate determination in cephalopods. Because of biological differences between species groups, not all techniques are applicable for every species. This review outlines the use of five main ageregistering structures (statoliths, gladii, beaks, stylets, and eye lenses) along with one chemical aging technique (lipofuscin) and their application to cephalopod species groups., SI

The present study was carried out to validate the daily deposition and age estimation by using beak rostrum sagittal sections increments of cultivated Octopus maya ( Voss and Solis, 1966 ). This study validates for first time the periodicity of beak increments by using animals of known age. We analyzed the rostrum sagittal sections (RSS) of upper and lower beaks in 40 juveniles of O. maya divided into four age groups (63, 87, 105 and 122 days) with 10 individuals per group. The animals were fed with a soft diet allowing obtaining age estimations not affected by the beak erosion. At the same time 50 animals were sampled every 20 days until 120 days old to obtain an age-body wet weight (BW) curve which could be compared with the age-BW curve obtained using age estimations from beaks. Co-variance analysis showed no statistical differences between both curves. The number of increments present in the beaks corresponded with the number of days from hatchling. Therefore, it was possible to validate that a growth increment corresponds to a day of life in O. maya , confirming that, up to 122 days old, the beaks counts can be used to determine the age of O. maya .

Age estimation of the cephalopod Octopus vulgaris by using beaks has improved in recent years, but maximum age and longevity in the wild have not been confirmed due to the low availability of senescent wild octopuses. In this study, a beak analysis of lateral wall surfaces (LWS) from 20 spent specimens confirmed the one-year lifecycle of the species in Central East Atlantic waters. Stress marks (checks) were clearly located in the daily increment sequence of rostrum sagittal sections (RSS). The highest daily variations in sea surface temperature (ΔT) that occurred during the last months of their lifetimes coincided with the locations of the marks on the beak, enabling confirmation of O. vulgaris beaks as life recorders for the first time. It also supports the daily deposition of RSS beak increments in the wild. Individuals were grouped into two main zones, at 20ºN and 18ºN respectively. Both groups showed different thermal check patterns, in accordance with the oceanographic differences. Two other checks (not coinciding with high values of ΔT) were observed in RSS at averages of 15 and 28 days before death, respectively, which were interpreted as responding to senescent-related events., Instituto Espanol de Oceanografia

Octopus vulgaris is a viable candidate for commercial aquaculture, but rearing procedures might stress individuals and result in diminished growth and survival. The present study investigated the relationship between possible stress sources (tank transposition and siphoning) when rearing O. vulgaris paralarvae and the deposition pattern of growth increments in their beak microstructure. Light intensity at the facility was heterogeneous, and accounted for with an experimental design consisting of blocks without replicates. Growth and survival were estimated and possible effects of handling were tested for both parameters. Increments and stress marks were counted in 120 paralarval upper jaws (UJ), and the number of UJs with a mark on the day of stress application (day 8) was quantified. Differences in light intensity, diet quantity, and total number of marks in the UJ were also compared between treatments. Growth and survival were statistically similar between treatments, although the control treatment showed a tendency for higher survival rates. Age at first increment deposition coincided with day 1 of experiment, and a 1 increment.day-1 deposition rate was validated for the experiment duration. The number of stress marks was significantly different between the control and other treatments, indicating that handling might cause stress and that marks can be used as a biomarker for stress, even though the occurrence of stress marks on day 8 was not significantly different. Light intensity and diet might have also been relevant stressors and confounded the results. The results herein presented are important for improving rearing conditions for O. vulgaris paralarvae.

Two methods are currently available for age estimation in octopus beaks. They have been applied to the same specimen from a sample of 30 individuals of Octopus vulgaris caught in central-eastern Atlantic waters. These techniques aim at revealing growth increments in the rostrum sagittal sections (RSS) and lateral wall surfaces (LWS) of octopus upper and lower beaks. Both methods were improved to reduce the time of sample preparation and to enhance the appearance of the increments. For each individual, two independent readings were done for upper and lower beak sections, as well as for the lateral wall surfaces. Vertical reflected light (epifluorescence) and image analysis system were shown to be useful in the observation and analysis of the sequence of increments. Precision of the ageing, increment counts obtained by both techniques, and increment widths were discussed. Using upper beak RSS led to more precise age estimates, whereas preparing LWS was quicker and simpler, and revealed a higher number of increments. Therefore, our study recommends counting growth increments in LWS of beaks to age adult, Sí

Coleoid cephalopod phylogeny is well studied via both molecular and morphological data, yet although some agreement has been reached (e.g. that extant Decapodiformes and Octopoda are monophyletic) many details remain poorly resolved. Fossil coleoids, for which much data exists, have hitherto not been incorporated into analyses. Their inclusion is highly desirable for the support of neontological phylogenies, to better reconstruct character-state histories, and to investigate the placement of the fossil groups themselves. In this study we present and analyse a morphological data matrix including both extinct and extant taxa. Homology assumptions in our data are discussed. Our results are presented both with and without the constraint of a monophyletic Decapodiformes imposed. When analysed with this constraint our results are strikingly congruent with those from molecular phylogeny, for instance placing Idiosepius in a basal position within Decapodiformes, and recovering Oegopsida and Bathyteuthoidea (although as grades). Our results support an Octopodiformes clade (“vampire squid” Vampyroteuthis as sister to Octopoda) and an octopodiform interpretation for most fossil coleoids. They suggest the fossil sister taxon to the octopods to be Plesioteuthididae. Most fossil higher taxa are supported, although many genera, especially within suborder Teudopseina, appear para- or polyphyletic., SI

12 pages, 4 figures, 4 tables., Egg masses of the loliginid squid Loligo vulgaris Lamarck, 1798 are attached to hard substratum or branched sessile organisms on the sea bottom. Embryonic development lasts from a few weeks to a few months, depending on the environmental water temperature. Because embryonic statolith growth of L. vulgaris is very sensitive to temperature under laboratory conditions, we analyzed the possibilities of determining past events in the squid¹s early life from analysis of the embryonic area of statoliths of wild squid populations. The relationship between egg-incubation temperature and daily growth of embryonic statoliths under laboratory conditions was determined by tetracycline markings at 10 incubation temperatures ranging from 12 to 24.7°C. In addition, the mean width of embryonic increments in statolith collections of wild L. vulgaris from the Eastern Atlantic (Saharan Bank and NW Iberian Peninsula) and the Mediterranean Sea (Central and Eastern) was calculated. The temperature inferred from the embryonic increment widths of the statoliths of wild squid indicates that embryonic development of L. vulgaris in the regions sampled is likely to occur at temperatures ranging from 12 to 17°C. Mediterranean squid have wider embryonic increments than Atlantic squid, reflecting the slightly higher water temperatures in the Mediterranean Sea during the development of the egg masses. Eggs of L. vulgaris spawned off the NW Iberian Peninsula were estimated, on average, to remain at sea for 47 d, 1 wk longer than Mediterranean eggs (nearly 1 mo longer when comparing minimum and maximum ranges). A longer incubation time for egg masses attached to the sea bottom increases mortality risks. Conversely, slow development at a lower temperature can improve yolk conversion, producing larger hatchlings, and increased hatching competence is expected from such squid. Therefore, a compromise between longer-versus-shorter incubation time and related characteristics does exist., This study was partially funded by the research project MAR95-1919-C05-04 of the Comisión Interministerial de Ciencia y Tecnología of Spain to R.V. and by the EU project CEPHSTOCK.

This study demonstrates the daily deposition of increments in Octopus vulgaris beaks for both lateral wall surfaces (LWS) and rostrum sagittal sections (RSS). Forty-nine marked wild animals kept in aquaria (weight range, 158–3,521 g) and 24 captive-reared known-age individuals (paralarvae, 0–98 days old; adults, 200–734 days old) were studied, encompassing for the first time the full age range of the species, including known-age individuals older than 1 mo. The daily deposition of beak increments was validated in the LWS by injection of Calcofluor, and in the RSS by environmental marking (thermal, confinement, capture, and stress of the chemical marking process). A total of 111 successful validations (when beak increments corresponded precisely to days elapsed) were achieved, and the maximum validated periods were 57 days (LWS) and 112 days (RSS). In the pelagic stage and transition to the settlement stage, a new pattern of microincrements that record age was demonstrated in the lateral hood surfaces of upper jaws, where stress checks were observed. In the benthic stage, tip erosion in beak RSS results in some underestimation of age; however, the demonstration that RSS can record environmental stress renders it a potentially useful tool for documenting life events., SI

The common octopus (Octopus vulgaris), a promising species for aquaculture, spawns easily under captivity from mature females (usually above 1 kg wet weight). Octopus juveniles and adults are collected from nature to obtain eggs and paralarvae for aquaculture development trials. In July 2011, a very small female (150 g wet weight but with an age estimation of 300 days-old) spawned almost 77,000 paralarvae. Malformations of paralarvae were noticed in the first spawning days, namely the absence of arms. Despite not being lethal, these abnormalities might be derived from the physiological condition of the breeding specimen (the female’s lower weight to the estimated amount of living days), which might be eventually related to nutritional unbalances or genetic parameters that were transferred to the eggs., Sí

The biological characteristics of the squid Loligo vulgaris from north France, north-west Portugal, the Saharan Bank, and the Greek Seas were analyzed to describe large-scale biological patterns and to evaluate geographical variation in the Atlantic and the Mediterranean. In northwest Portugal and on the Saharan Bank population length structures are more complex due to extended spawning and recruitment periods. Squid spawn only between November and April in north France and the Greek Seas. Gonadosomatic indices decreased with decreasing latitude in the Atlantic, while the highest indices were found in the Mediterranean. Full maturity occurred at smaller size in northwest Portugal than in other areas of the Atlantic, and at similar size to Mediterranean squid. Length-weight relationship slopes increased from the north to the south in the Atlantic and in the Mediterranean. Multivariate analysis of seasonal biological indices demonstrated significant biological differences between squid of different areas, mainly in terms of size at maturity, male GSI and average body size and weight. Biological variability between areas was considered related to plasticity of responses to large-scale geographic environmental conditions., Sí