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.

The early life history traits of the labrisomid blenny Auchenionchus crinitus (Jenyns, 1842) from subtidal rocky reefs were studied, based on microstructure analysis of sagittae of their pelagic larvae (4.01 mm NL −12.50 mm SL). Ichthyoplankton was collected in shallow (<20 m) nearshore waters off Isla Santa María, Antofagasta, northern Chile every 15 days during austral autumn–winter 2014 (five sampling days). During late May and early June, larval abundance was low (median ± MAD, 39.06 ± 5.08 ind. 100 m−3), increasing significantly during mid-June to early August (110.98 ± 47.66 ind. 100 m−3). Using 354 sagittae, the back-calculated hatch dates indicated the occurrence of three hatching events, two in autumn and one in winter. Hatching occurred mainly during the illuminated phases of the lunar cycle. All three batches had similar estimated larval sizes at hatch (3.2–3.7 mm SL), as well as similar growth rates (0.19–0.22 mm day−1) during the first 30 days of life. During the study period, shallow waters were well mixed, with seawater temperature of 14.73 ± 0.58°C and salinity of 34.84 ± 0.04. This is the first estimation of early life history traits of this cryptobenthic species from rocky reefs of Chile.

To study some early life history traits of Lipophrys pholis, 110 recruits (TL ≤ 30 mm) were collected in April and May 2013 during the low tide periods in four rocky beaches along the west (Cabo do Mundo, Peniche and Vale do Homem) and south (Olhos de Água) Portuguese coasts. Pelagic larval duration, size at settlement and age at coastal recruitment were back-calculated from the microstructure of otoliths. Pelagic larval duration estimated from micro-increment counts until the settlement marks ranged from 57 to 73 days and showed a latitudinal reduction trend from north to south. This variable seems to be related in 30% with the regional seawater temperatures probably through the direct effect on the somatic growth. Settlement sizes (~19 mm) did not show any regional differences suggesting that this is a more conservative character within species. The mean age at coastal recruitment varied between 69 and 93 days, but northern individuals were recruited at an older age. Back-calculated spawning, hatching and settlement dates appear to be unrelated to the lunar cycle for L. pholis.

Otolith microstructure analysis was used to reveal daily growth patterns of young-of-the year (YOY) of six species of perciform fishes, Bovichtus chilensis (Bovichtidae), Girella laevifrons and Graus nigra (Kyphosidae), Helcogrammoides chilensis (Tripterygiidae) and Hypsoblennius sordidus and Scartichthys viridis (Blenniidae). YOY collected in intertidal pools from June to December 2008 in Central Chile, ranged from 24 to 76 mm total length and from 25 to 390 days of age. In the six species, sagittal otoliths showed a slightly oval shape, symmetrical and laterally compressed and showed micro-increments distinguishable after a two-side polishing. Increment width of sagittae showed two patterns irrespective of hatch month and species: (i) a parabolic growth with wider increment widths (during the first 150 of YOY life, e.g. B. chilensis, G. nigra and G. laevifrons); and (ii) a more irregular pattern with lower increment widths during most of the seasons in H. chilensis and H. sordidus. Further results were: (i) a unique central primordium enclosed by two checks after which distinctive increments were deposited; (ii) low instantaneous growth rates estimated through the slope of the length-at-age relationship (range 0.1–0.21 mm d−1); and (iii) a linear fish size–otolith size relationship.