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Presenting all bodies of work contained in the Xenogenesis exhibition, this publication includes many materials and graphics from The Otolith Group's (Anjalika Sagar and Kodwo Eshun) broader practice, including performance, lecture and research material. The outcome of over four years of collaboration, research and conversation, the publication is not a chronological exhibition catalogue or retrospective but a cross-section of their work which includes substantial contributions from the artists themselves, in the form of writing and direct engagement with its production. The publication also brings together important thinkers, scholars, art historians and writers from disparate fields, who know and have worked with the group, as well as those who are writing from a contemporary perspective. They include Dr. Denise Ferreira da Silva, Annie Fletcher, Anselm Franke, Shanay Jhaveri, George E. Lewis, Mahan Moalemi, Fred Moten, Grant Watson, Vivian Ziherl and the late Mark Fisher each of whom reflect on a particular aspect of the Group's practice with supplementary materials such as archival images, documented conversations, early lecture performances as well as other accompanying texts and examinations of their research sites. Published by Irish Museum of Modern Art and Archive Books, with the generous support of the international partners and tour venues, Buxton Contemporary, Haus der Kulturen der Welt (HKW), Institute of Contemporary Art, Virginia, Sharjah Art Foundation, Southern Alberta Art Gallery and Van Abbemuseum. Exhibition: Irish Museum of Modern Art, Dublin, Ireland (09.10.2020 - 17.01.2021).

This study is the first to investigate the intra- and interspecific differences in otolith’s length (Lo), width (Wo), perimeter (Po), area (Ao), and mass asymmetry (OMA) in the pelagic Ethmalosa fimbriata, demersal Galeoides decadactylus, and benthic Cynoglossus monodi collected from the Lebe fishing site located along the Komo Estuary, central-western Gabon. The objectives were to (1) verify whether or not otolith morphometry differs in relation to living depth levels of the three species, (2) examine fluctuating asymmetry (FA) in the otolith morphometry, and (3) assess the relationship between OMA and total length (TL). A significant asymmetry was found in Lo, Wo, Po, and Ao between the left and right otoliths within and among males and females at the intraspecific level and only in Wo and Ao at the interspecific level due to FA. At the intraspecies level, a significant OMA was only observed within females of G. decadactylus and C. monodi and males and females of E. fimbriata and C. monodi. Moreover, a significant relationship between OMA and TL was detected only among males and females within the pelagic E. fimbriata and the demersal G. decadactylus, and no significant relationship was found at the interspecific level. As a result, significant differences in Wo and Ao and non-significant differences in OMA were recorded between the three species based on variations in living depth levels. These results highlight the importance of using otolith morphometry and OMA analyses to address the relationship between fish species and their living depth levels.

Presenting all bodies of work contained in the Xenogenesis exhibition, this publication includes many materials and graphics from The Otolith Group's (Anjalika Sagar and Kodwo Eshun) broader practice, including performance, lecture and research material. The outcome of over four years of collaboration, research and conversation, the publication is not a chronological exhibition catalogue or retrospective but a cross-section of their work which includes substantial contributions from the artists themselves, in the form of writing and direct engagement with its production. The publication also brings together important thinkers, scholars, art historians and writers from disparate fields, who know and have worked with the group, as well as those who are writing from a contemporary perspective. They include Dr. Denise Ferreira da Silva, Annie Fletcher, Anselm Franke, Shanay Jhaveri, George E. Lewis, Mahan Moalemi, Fred Moten, Grant Watson, Vivian Ziherl and the late Mark Fisher each of whom reflect on a particular aspect of the Group's practice with supplementary materials such as archival images, documented conversations, early lecture performances as well as other accompanying texts and examinations of their research sites. Published by Irish Museum of Modern Art and Archive Books, with the generous support of the international partners and tour venues, Buxton Contemporary, Haus der Kulturen der Welt (HKW), Institute of Contemporary Art, Virginia, Sharjah Art Foundation, Southern Alberta Art Gallery and Van Abbemuseum. Exhibition: Irish Museum of Modern Art, Dublin, Ireland (09.10.2020 - 17.01.2021).

Biogeochemical tracers found in the hard parts of organisms are frequently used to answer key ecological questions by linking the organism with the environment. However, the biogeochemical relationship between the environment and the biogenic structure becomes less predictable in higher organisms as physiological processes become more complex. Here, we use the simultaneous combination of biogeochemical tracers and fish growth analyzed with a novel modeling framework to describe physiological and environmental controls on otolith chemistry in an upwelling zone. First, we develop increasingly complex univariate mixed models to describe and partition intrinsic (age effects) and extrinsic (environmental parameters) factors influencing fish growth and otolith element concentrations through time. Second, we use a multivariate mixed model to investigate the directionality and strength between element-to-element and growth relationships and test hypotheses regarding physiological and environmental controls on element assimilation in otoliths. We apply these models to continuous element (Na, Sr, Mg, Ba, Li) and growth increment profiles (monthly resolution over 17 yr) derived from otoliths of reef ocean perch (Helicolenus percoides), a wild-caught, site-attached, fully marine fish. With a conceptual model, we hypothesize that otolith traits (elements and growth) driven by environmental conditions will correlate both within an otolith, reflecting the time dependency of growth and element assimilation, and among individuals that experience a similar set of external conditions. We found some elements (Sr:Ca and Na:Ca) are mainly controlled by physiological processes, while other elements (Ba:Ca and Li:Ca) are more environmentally influenced. Within an individual fish, the strength and direction of correlation varies among otolith traits, particularly those under environmental control. Correlations among physiologically regulated elements tend to be stronger than those primarily controlled by environmental drivers. Surprisingly, only Ba:Ca and growth are significantly correlated among individuals. Failure to appropriately account for intrinsic effects (e.g., age) led to inflated estimates of among individual correlations and a depression of within individual correlations. Together, the lack of among-individual correlations of otolith traits in properly formulated models and the biases that can be introduced by not including appropriate intrinsic covariates suggest that caution is needed when assuming multi-elemental signatures are reflective solely of shared environments.

A total of 243 Pagellus erythrinus saccular otoliths’ shape and size, including length, width, area, and perimeter, were examined among individuals of the Chebba, Sfax, Gabes, and Zarzis stations located in the Gulf of Gabes, Tunisia. The objective was to assess the geographic variation in the otoliths' shape and size and the effect of potential fluctuating asymmetry in otolith size on the stock structure of P . erythrinus individuals from these stations. Analysis of the otolith shape showed a statistically significant difference (Wilks’ λ = 0.1661, p < 0.0001), i.e., asymmetry, in the left and right otoliths shape among individuals of the four stations, as well as among those within the Chebba and Gabes stations. Besides, a significant shape difference was observed in the left-left and right-right otoliths among individuals of both Chebba and Gabes, Chebba and Zarzis, Gabes and Sfax, Gabes and Zarzis, and Sfax and Zarzis stations. Moreover, a significant fluctuating asymmetry was detected in width between the left and right otoliths only among individuals of the Sfax and Gabes stations. Discriminant function analysis of the otoliths’ contour shape confirmed the presence of three separate main stocks, one corresponding to the Chebba and Sfax stations, the second representing Gabes, and the third characterizing Zarzis, which should be managed separately.

Variations in sagittal otolith shape and morphometry, including length (Lo), width (Wo), area (Ao), and perimeter (Po), were investigated in two populations of Chelon ramada collected from the Boughrara and El Bibane lagoons located in southeastern Tunisia. The objective was to assess the geographic variation in the sagittal otoliths' shape and morphometry and the effect of potential fluctuating asymmetry (FA) in morphometry on the stock structure of C. ramada in the two lagoons to inform on appropriate management procedures. At the interpopulation level, analysis of sagittal otolith shape showed a statistically significant difference (P = 0.0001), i.e. there was a bilateral asymmetry, in the shape of left and right otoliths between individuals of the two populations. In addition, significant FA was found only in Lo between the left and right otoliths. At the intrapopulation level, a significant shape difference (P < 0.0001), particularly asymmetry, was observed in both left and right otoliths between males and females, indicating sexual dimorphism in shape within the Boughrara lagoon. However, significant shape similarity, i.e. symmetry, was observed in the left and right otoliths among individuals of the El Bibane lagoon. Moreover, a significant FA was detected in Lo between the left and right otoliths only among males, as well as between males and females of the Boughrara lagoon. However, a significant FA between the left and right otoliths was found only in Wo among males and in all morphometric dimensions among females and Wo between males and females of the El Bibane lagoon. Discriminant function analysis of the otolith contour shape confirmed the presence of two separate C. ramada stocks, one corresponding to the Boughrara lagoon and the other representing the El Bibane lagoon, which should be managed separately. The possible cause of morphological variation in the sagittal otoliths' shape and morphometry due to FA between individuals of the two populations was discussed in relation to the biotic and abiotic factors.

Otolith morphological and microchemical analyses are relatively new scientific research methods used in fish stock evaluation and management. However, in Tunisia, only morphological methods have been used. The objective of this study was the Sarpa salpa stock discrimination of Djerba and Kerkennah by the otoliths morphological and microchemical analysis, while carrying out a fluctuating asymmetry analysis and a stock comparison of males and females for each population. The results revealed significant differences between the Djerba and Kerkennah populations, significant differences between the stocks of males and females in each population, and a highly significant fluctuating asymmetry for both populations. The results of the otolith morphological analysis were similar to those of the microchemical analysis. This result proves that both morphological and microchemical analyses are powerful tools for fish stock discrimination.

Chemical analysis of calcified structures continues to flourish, as analytical and technological advances enable researchers to tap into trace elements and isotopes taken up in otoliths and other archival tissues at ever greater resolution. Increasingly, these tracers are applied to refine age estimation and interpretation, and to chronicle responses to environmental stressors, linking these to ecological, physiological, and life-history processes. Here, we review emerging approaches and innovative research directions in otolith chemistry, as well as in the chemistry of other archival tissues, outlining their value for fisheries and ecosystem-based management, turning the spotlight on areas where such biomarkers can support decision making. We summarise recent milestones and the challenges that lie ahead to using otoliths and archival tissues as biomarkers, grouped into seven, rapidly expanding and application-oriented research areas that apply chemical analysis in a variety of contexts, namely: (1) supporting fish age estimation; (2) evaluating environmental stress, ecophysiology and individual performance; (3) confirming seafood provenance; (4) resolving connectivity and movement pathways; (5) characterising food webs and trophic interactions; (6) reconstructing reproductive life histories; and (7) tracing stock enhancement efforts. Emerging research directions that apply hard part chemistry to combat seafood fraud, quantify past food webs, as well as to reconcile growth, movement, thermal, metabolic, stress and reproductive life-histories provide opportunities to examine how harvesting and global change impact fish health and fisheries productivity. Ultimately, improved appreciation of the many practical benefits of archival tissue chemistry to fisheries and ecosystem-based management will support their increased implementation into routine monitoring.

The current study aims to calculate and assess the asymmetry of the two goatfish species, Yellowstripe goatfish (Lacepède 1801) and Red Sea goatfish, (Fourmanoir & Guézé 1976) collected from Hurghada fishing harbour, Egypt. The asymmetry valuation for . and is imperative to demonstrate the impact of asymmetry on the larvae settlement in this vital fishing ground. Asymmetry was calculated for the saccular otolith (Sagittae) biometry, namely length, width, and mass. The results showed that the otolith height had a lower asymmetry value than the otolith length for the two goatfish species inspected. No relationship between the asymmetry value of otolith length and width and total fish length was observed. Both goatfish species’ calculated otolith mass asymmetry was higher than that of many teleost fish species.

Yellowfin tuna Thunnus albacares is a highly exploited species in the Indian Ocean. Yet, its stock structure is still not well understood, hindering assessment of the stock at a suitable spatial scale for management. Here, young-of-the-year (<4 mo) yellowfin tuna otoliths were collected in 2018 and 2019, from 4 major nursery areas in the Indian Ocean: Madagascar, Seychelles-Somalia, Maldives and Sumatra. First, direct age estimates were made in a subset of otoliths by visually counting microincrements to identify the portion of the otolith corresponding to the larval stage. We then developed 2-dimensional maps of trace element concentrations to examine spatial distribution of elements across otolith transverse sections. Different distribution patterns were observed among the elements analysed; Li, Sr and Ba were enriched in the portion of the otolith representing early life, whereas Mn and Mg concentrations were heterogeneous across growth bands. Last, we analysed inter-annual and regional variation in otolith chemical composition using both trace elements (Li, Mg, Sr, Ba and Mn) and stable isotopes (δ13C and δ18O). Significant regional variation in otolith chemical signatures was detected among nurseries, except between Madagascar and Seychelles-Somalia. Otolith δ13C and δ18O were important drivers of differentiation between western (Madagascar and Seychelles-Somalia), Maldives and Sumatra nurseries, whereas the elemental signatures were cohort specific. Overall nursery assignment accuracies were 69−71%. The present study demonstrates that baseline chemical signatures in the otoliths of yellowfin tuna are regionally distinct and can be used as a natural tag to investigate the nursery origin of older individuals in the Indian Ocean.