Survival rates of rays discarded by the bottom trawl squid fishery off the Falkland Islands

Waters off the Falkland Islands are subject to a specialized multispecies ray fishery and were first fished by a Korean fleet in 1989. More than twenty different rajid species have been recorded from catches around the islands, and five species accounted for 87.04% of the total catch during 1993−2002. Catches peaked in 1993 at 8523 metric tons, and specific fishing licenses — R (second season) and F (first season) — were first introduced in 1994 and in 1995, respectively (Agnew et al. 2000; Falkland Islands Government, 2002; Wakeford et al., in press)

Innovative use of sclerochronology in marine resource management

In recent years, technical and analytical developments in sclerochronology, based on the analysis of accretionary hard tissues, have improved our ability to assess the life histories of a wide range of marine organisms. This Theme Section on the innovative use of sclerochronology was motivated by the cross-disciplinary session ‘Looking backwards to move ahead—how the wider application of new technologies to interpret scale, otolith, statolith and other biomineralised age-registering structures could improve management of natural resources’ convened at the 2016 ICES Annual Science Conference in Riga, Latvia. The contributions to this Theme Section provide examples of applications to improve the assessment and management of populations and habitats, or showcase the potential for sclerochronology to provide a deeper understanding of the interaction between marine life and its environment, including the effects of changing climate

Fecundity of the common cuttlefish, Sepia officinalis L. (Cephalopoda, Sepiida): a new look at the old problem

The potential fecundity (PF) of advanced maturing and mature pre-spawning cuttlefish S. officinalis in the Aegean Sea varies from 3,700 to 8,000 (mean 5,871) oocytes, whereas the number of large yolk oocytes increases with mantle length from 130 to 839. Small oocytes predominate at all maturity stages. Spawning animals have a PF of some 1,000-3,000 eggs below that of pre-spawning females. This shows that intermittent spawning, which occurs in captivity, is a normal process in natural habitats. Empty follicular sheaths are resorbed very rapidly, and their number does not represent the number of eggs laid by the female prior to sampling. Regulative oocyte resorption was observed at early maturation in some cuttlefishes

Dwarf males of giant warty squid Kondakovia longimana and a description of their spermatophores

Antarctic squids are widely known to play an important role in the diet of various Antarctic predators, although the biology of those squids and how that relates to their availability to their predators is poorly known. We assessed the reproductive system of the deep-sea giant warty Antarctic squid Kondakovia longimana under a predator–prey context. The spermatophores of male K. longimana are described, based on two specimens foraged by albatrosses at Bird Island, South Georgia (54°S, 38°W). Spermatophore length (SL) was 42–90 mm, head occupied mean = 1.8–2.4% SL, ejaculatory tube = 17–22% SL, cement body = 19–22% SL, seminal reservoir = 56–59% SL and rear empty part = 0.4–0.8% SL. All spermatophores of K. longimana in our study were normal and functional, and very dissimilar to those of other spent squid, in which the spermatophores have short, semi-transparent seminal reservoirs and a large empty rear part. Senescent male K. longimana could become available to predation by albatrosses (presumably being surfaced) with spermatophoric sacs (Needham’s sacs) containing at least a hundred of normal spermatophores having no evidence of reproductive system degeneration. From known relation between beak and body size all known adult males in K. longimana were dwarfs in respect to females. Our data also show that they have extended spermatophore production as in other squids

Growth, reproduction and feeding of the tropical squid Ornithoteuthis antillarum (Cephalopoda, Ommastrephidae) from the central-east Atlantic

Length composition, age, growth, reproductive biology, feeding and parasites were studied using 432 individuals of the squid Ornithoteuthis antillarum (1.8-138 mm ML) collected in the open waters of the tropical central-east Atlantic. In the region studied, only a small-sized and early-maturing population of O. antillarum occur. Statolith shape, development and microstructure have several peculiar features setting O. antillarum apart of other ommastrephids. Assuming growth increments within statoliths to be daily, maximum age of squids does not exceed 182 days. Growth rates of juveniles and immature squids are high and similar to another fast-growing ommastrephid Sthenoteuthis pteropus, but they decrease considerably with the onset of maturation. Potential fecundity varies from 50,000 to 220,000 oocytes. It is suggested that the squid is a multiple spawner with frequent releases of small-sized (No disponibl

Cephalopod embryonic shells as a tool to reconstruct reproductive strategies in extinct taxa

© 2017 Cambridge Philosophical Society.An exhaustive study of existing data on the relationship between egg size and maximum size of embryonic shells in 42 species of extant cephalopods demonstrated that these values are approximately equal regardless of taxonomy and shell morphology. Egg size is also approximately equal to mantle length of hatchlings in 45 cephalopod species with rudimentary shells. Paired data on the size of the initial chamber versus embryonic shell in 235 species of Ammonoidea, 46 Bactritida, 13 Nautilida, 22 Orthocerida, 8 Tarphycerida, 4 Oncocerida, 1 Belemnoidea, 4 Sepiida and 1 Spirulida demonstrated that, although there is a positive relationship between these parameters in some taxa, initial chamber size cannot be used to predict egg size in extinct cephalopods; the size of the embryonic shell may be more appropriate for this task. The evolution of reproductive strategies in cephalopods in the geological past was marked by an increasing significance of small-egged taxa, as is also seen in simultaneously evolving fish taxa

The importance of cephalopods in the diet of fish on the northwest European shelf.

Cephalopods are universal to the world's oceans and prey to many fish species. On the northwest European shelf, integrated ecosystem assessments are rapidly evolving into the preferred method for holistically assessing stocks, but cephalopods appear to be an overlooked component, perhaps because their roles in ecosystems have seldom been quantified in recent years. We have analysed historical fish stomach records and revisited literature at local and regional level to determine the importance of cephalopods to the diets of 26 ecologically important finfish. We conclude that, in contrast to most other large marine ecosystems, cephalopods found in the Greater North Sea and the Celtic Seas regions appear to contribute only a small fraction to the diets of ecologically important finfish (found in the stomachs of ~14% of specimens among some species, but generally only 1–3% in most species), though their role as predator may be important and require further investigation. Based on our findings, cephalopods may not represent a key component for integrated ecosystem assessments, though as squid populations have been shown to expand throughout the North Sea in recent years, regular monitoring is encouraged to identify the point where their inclusion into such models may be necessary

Micro-scale geochemical and crystallographic analysis of Buccinum undatum statoliths supports an annual periodicity of growth ring deposition

The whelk Buccinum undatum is commercially important in the North Atlantic. However, monitoring the ontogenetic age and growth of populations has been problematic for fisheries scientists owing to the lack of a robust age determination method. We confirmed the annual periodicity of growth rings present in calcified statoliths located in the foot of field-collected and laboratory reared whelks using microscale measurements of trace element geochemistry. Using Secondary Ion Mass Spectrometry (SIMS), annual trace element profiles were quantified at 2 μm resolution in statoliths removed from whelks collected alive from three locations spanning the length of the UK; the Shetland Isles (North), the Menai Strait, North Wales (Mid) and Jersey (South). Clear cycles in the Mg/Ca ratio were apparent with minimum values corresponding with the visible dark statolith rings and comparatively higher ratios displayed in the first year of growth. Statoliths from one and two-year-old laboratory reared whelks of known age and life history contained one and two Mg/Ca cycles respectively and demonstrated that the statolith growth ring is formed during winter (February and March). Cycles of Na/Ca were found to be anti-correlated to Mg/Ca cycles, whilst ratios of Sr/Ca were inconsistent and showed an apparent ontogenetic increase, suggesting strong physiological control. Variability in elemental data will likely limit the usefulness of these structures as environmental recorders. The results obtained using SIMS for trace element analysis of statoliths confirms the robustness of the statolith rings in estimating whelk age. μXRD at 2 μm spatial resolution demonstrated the statoliths were wholly aragonitic and thus trace element variation was not the result of possible differences in CaCO3 polymorph within the statolith. Changing XRD patterns along with SEM imaging also reveal an ‘hourglass’ microstructure within each statolith. The validation of the annual periodicity of statolith growth rings now provides a robust and novel age determination technique that will lead to improved management of B. undatum stocks

Vampire squid reproductive strategy is unique among coleoid cephalopods

Coleoid cephalopods are thought to go through only one reproductive cycle in their life. We here report that vampire squid (Vampyroteuthis infernalis) show evidence of multiple reproductive cycles. Female vampire squid spawn their eggs, then return to a resting reproductive state, which is followed by the development of a new batch of eggs. This reproductive cycle is likely to be repeated more than twenty times. This combination of reproductive traits is different from that of any other extant coleoid cephalopod

Age and growth rate estimations of the commercially fished gastropod Buccinum undatum

Calculating age and growth rate for the commercially important whelk, Buccinum undatum in the aid of fishery management has historically been undertaken using growth rings on the organic operculum. This is difficult due to their poor readability and confusion between two different sets of growth lines present. Recent work presented the calcium carbonate statolith as an alternative for age determination of B. undatum. Here we compare the use of statoliths and opercula, comparing their readability and creating growth curves for three distinct populations across the United Kingdom. Using these data, we also test the most appropriate growth equation to model this species. Lastly, we use oxygen isotope analysis of the shells to assign accurate ages to several individuals from each site. These data were used to test the accuracy of statolith and operculum ages. Statoliths, whilst more time consuming to process have improved clarity and accuracy compared with the opercula. This improved readability has highlighted that a Gompertz growth function should be used for populations of this species, when in past studies, von Bertalanffy is often used. Statoliths are a viable improvement to opercula when assessing B. undatum in the context of fishery monitoring and management