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In teleosts, biometric parameters of certain bony structures are used for the age and/or size determination of the fish. Otolith is perhaps the most widely used of these bony structures. There are numerous studies which have shown that otolith biometry is positively and strongly correlated with fish size. In this paper, some recent studies that investigate the relationship between otolith biometry and fish length are summarized. It is possible to estimate fish size and/or age by knowing this relationship. This information can be useful, especially when it is not possible to sample a certain portion of a fish population. Besides, otoliths found in archaeological excavation sites or in the stomachs of predators can provide information about the fish they belong to. These data are useful to taxonomists, paleobiologists, and researchers studying the nutritional biology of predators.

Relationships between fish length and otolith length, width and mass were examined in the Australian anchovy Engraulis australis (White, 1790) recovered from the food of Gannet examined from colonies at islands of Horuhoru Rock and Mahuki Islands in the Hauraki Gulf, New Zealand. The relationships between otolith length- fish total length (TL), otolith-weight-TL, and otolith-width-TL were investigated by means of non-linear regression models (TL = 0.54 OL 16.86, TL = 4.39 OW 7.61 and TL = 26.19 OWe 2.2). This study characterizes the first reference available on the relationship of fish size and otolith size and weight for E. australis obtained from bird’s food in the Pacific Ocean region

Methylmercury (MeHg) is a neurotoxic pollutant that bioaccumulates and biomagnifies in aquatic food webs, impacting the health of piscivorous wildlife and human consumers of predatory fish. While fish mercury levels have been correlated with various biotic and abiotic factors, many studies only measure adults to characterize the health of locally fished populations, omitting information about how local fish bioaccumulate mercury relative to their growth. In this study, we sought to establish length: total mercury (THg) concentration relationships in juvenile and adult fish of four genera (sunfish, yellow perch, white perch, and killifish) across six freshwater pond systems of Nantucket Island to determine safe consumption sizes across species and environmental conditions. A wide length range (2-21 cm) was utilized to develop linear regression models of ln-THg versus fish length. In most cases, different genera within the same pond indicated similar slopes, supporting that all four genera share comparable features of feeding and growth. Comparing individual species across ponds, differences in ln-THg versus fish length were attributable to known environmental Hg-modulators including surface water MeHg levels, pH, and watershed area. Referencing human health and wildlife criteria, our results confirm that numerous Nantucket freshwater ecosystems contain elevated fish THg levels, which could impact the health of not only piscivorous wildlife in all measured ponds but also recreational fishers in at least two measured systems. Future studies should measure THg levels across juvenile and adult fish to detect potential differences in the slope of THg concentration across fish length relevant for local consumption advice.

Length and weight data for three species of fish Oreochromis niloticus, Lates niloticus, and Sydontus victorianus was collected from three East African lakes, Lake Victoria, Lake Baringo and Lake Naivasha. Correlation were done on weight and length based on the fish species, the lake collected from, sex, and the age. Correlation was found not to be a good measure of evaluating length weight relationship. Models had to be applied. Linear models, random regression models, proportional hazard models and threshold models. Random regression model was found to capture most of the information though it excluded the age of the fish on mean sum of squares error. The challenge with this is that it’s a long-term model which accounts for hatching to last date of the fish life.

This study was purposed to determine the optimal dose addition of potassium diformate to commercial feed to increase the growth of giant freshwater shrimp. The method employed in this study was an experimental method, embracing application of a Randomized Block Design (RBD) method. It consists of four treatments and four replications. The treatments was based on the difference of potassium diformate amount in which given to giant freshwater shrimp. The difference of potassium diformate amount was 0% (control), 1%, 3%, and 5%. The sample of study used giant freshwater shrimp with a length of 4 - 6 cm. The samples were obtained from the Giant freshwater Shrimp Breeding Center, Pamarican, West Java Province. The shrimp were kept in 16 nets in a density of 20 shrimps and the size of the net cage is about 1 m3. The parameters observed in this research were daily growth rate, feed efficiency, the relation between length and weight, survival rate (analyzed using ANOVA with p < 0,05), and water quality. The sampling was made every 10 days. The results showed that the addition of potassium diformate by 1% gave the best result of daily growth rate of 1.86% ± 0.60, feed efficiency value of 19% ± 1.91, survival rate of 92% with net profit Rp. 67.160.- and for the length and weight relationship has a value of b> 3 which means that it has positive allometry along with water quality parameters regarded to SNI (Indonesian national standard).

The aquaculture industry is one of the faster growing sectors of primary production. In recent years, innovative systems and high precision methodologies have been developed, improving all the aspects of production including fish living conditions. Fish biomass estimation is a key factor for husbandry, as it affects operation cost and final production. Here we propose a system that uses a stereo camera and machine vision/artificial intelligence algorithms to estimate the fish size of the Gilthead seabream and the European seabass in aquaculture cages. The system, without human intervention, acquires synchronized images from both cameras and by using a convolutional neural network, detects key measurement points on fish (snout, eye, pelvic fin and fork tail). To train the key-point detection network we created a dataset of manually annotated fish images. Given the fish body-parts (key-points), stereoscopy is used to estimate the fish length. The system was evaluated on a real dataset containing images from cage farms with known fish length distribution. The system achieved high accuracy in length estimation with mean relative length error of Gilthead seabream and the European seabass of 3.15% and 7.4%, respectively.

The present study was conducted to investigate the relationships between fish length, otolith size and otolith weight. A total of 180 Sperata aor and 171 Labeo bata specimens were collected monthly during January 2016 to March 2017 from the River Ganga at the Narora site. Student’s t-test showed no significant differences in the size of right and left otoliths in the selected fish species, therefore, a single linear regression based on the left otolith was carried out. Fish length was plotted against otolith weight, otolith length and otolith height. Moreover, otolith length was plotted against otolith weight and otolith height. The linear regression model was found to fit the data well for fish length to otolith size in both selected fish species. A strong relationship between otolith length and weight was found in both species (r2 > 0.8). Furthermore, the study revealed that fish length is potentially related to otolith size and a strong relationship between fish length and otolith size exists in S. aor (mean r2 = 0.89) as compared to L. bata (mean r2 = 0.70). Such relationships should be determined for the fish species that are ecologically and socio-economically important in order to understand their trophic relationships, population dynamics and yield estimates.

Otolith morphology analysis is one of the main tools used for fish or fish stock identification. Moreover, otolith shape can also be used in fish dietary studies (stomach content) for the identification of prey fishes and their size according to the relationship between fish and otolith sizes. In the present study, the relationship between fish length and otolith morphological dimensions was investigated for the sabre squirrelfish, Sargocentron spiniferum (Forsskål, 1775) (family: Holocentridae). Samples of 185 fish were collected from the coast of the Red Sea, Egypt. To analyze the relationship between fish and otolith, otolith morphometric measurements (length, width, area, perimeter, weight, sulcus, and ostium) and shape factors (aspect ratio, compactness, form factor, rectangularity, roundness, ellipticity, squareness) describing outline shape were extracted using image analysis. Generalized linear models were applied for the relationship between body length and each otolith morphology feature. From the relationships between the total length of fish and fourteen morphology features, only otolith length, caudal length, and squareness were significantly correlated with fish size. Our results provide more information for the relationship between fish length and otolith morphometric features.

Otolith morphology analysis is one of the main tools used for fish or fish stock identification. Moreover, otolith shape can also be used in fish dietary studies (stomach content) for the identification of prey fishes and their size according to the relationship between fish and otolith sizes. In the present study, the relationship between fish length and otolith morphological dimensions was investigated for the sabre squirrelfish, Sargocentron spiniferum (Forsskål, 1775) (family: Holocentridae). Samples of 185 fish were collected from the coast of the Red Sea, Egypt. To analyze the relationship between fish and otolith, otolith morphometric measurements (length, width, area, perimeter, weight, sulcus, and ostium) and shape factors (aspect ratio, compactness, form factor, rectangularity, roundness, ellipticity, squareness) describing outline shape were extracted using image analysis. Generalized linear models were applied for the relationship between body length and each otolith morphology feature. From the relationships between the total length of fish and fourteen morphology features, only otolith length, caudal length, and squareness were significantly correlated with fish size. Our results provide more information for the relationship between fish length and otolith morphometric features.

Sorting catfish manually requires a lot of time, yet it presents low accuracy. Export catfish farmers need better instruments to increase the yield of sorted catfish. Using the right method of image processing is one of the ways. Length is one of the parameters of export quality catfish. Somehow measuring the length is challenging as catfish has very smooth and flexible body. By using interpolation method and aerial image capturing technique, the average error is pretty small, only 5.97%.

High frequency multi-beam sonars enable the determination of fish size characteristics and behaviour in highly turbid and low-light conditions when more traditional methods, such as underwater cameras, are unsuitable. We sought to validate this technology, commonly referred to as imaging sonar, by determining its accuracy and precision during the measurement of small-bodied fish typical of coastal and estuarine environments. Validation was conducted in three ways: (1) a comparative tank-based validation of an Adaptive Resolution Imaging Sonar (ARIS) and stereo-camera measurements using two species of live fish, and synthetic targets; (2) assessment of the imaging sonar’s utility when measuring four different fishes possessing a range of swimming modalities, including labriform, sub-carangiform, and carangiform; and (3) comparison of field-based sonar sampling with conventional baited trap methodology. Our results showed that the angle at which targets are presented to the sonar beams caused measurement error during tank-based determinations. When this was factored into measurement protocols there was no significant interactive effect of swimming mode on measurement accuracy, with the sonar results between 0.3 and 9.6% in all four species investigated. Sonar derived measurements were less accurate and precise when compared to stereo-camera techniques. Field-based sampling outcomes were broadly comparable between the imaging sonar and baited trap sampling methodology. The suitability of the imaging sonar is discussed in the context of use in fish sampling surveys, particularly diurnal and nocturnal sampling regimes, and in turbid environments. Results validate the usefulness of imaging sonars for use in diverse fields of fisheries research.

In the study, the relationship between fish size and otolith measurements in the Fries's goby ( Lesueurigobius friesii ) were investigated. Fish specimens were collected by trawl operations from Izmir Bay between September 2005 and August 2006. A total of 100 Lesueurigobius friesii specimens were used for the study. Their total lengths (TL) and weights were recorded by a fish ruler and a digital scale with an accuracy of 0.1 cm and 0.01 g respectively. After that the fish were dissected and their sagittal otoliths were removed. Otolith lengths and heights were measured with an Olympus SZ61 stereo microscope with a micrometric ocular. Otoliths were weighted by a digital scale with an accuracy of 0.0001 g. The specimens used in the analysis were ranged between 5.5 and 8.7 cm total length and from 14.8 to 56.4 g in total weight. The length–weight relationship equations were estimated as W=0.0927*L 2.9431 (r=0.942). Otolith length (OL), otolith height (OH) and otolith weight (OW) of the species were ranged between 2.6–4.1 mm, 2.2–3.4 mm and 0.0049–0.0204 g, respectively. The total length–otolith length, total length–otolith height and otolith length–otolith height measurements showed significant linear relationships. The relations between the otolith weight–otolith length total length–otolith weight were found to be exponential.

Videogrammetry and photogrammetry are increasingly being used in marine science for unsupervised data collection. The camera systems employed are complex, in contrast to “consumer” digital cameras and smartphones carried by potential citizen scientists. However, using consumer cameras in photogrammetry will introduce unknown length estimation errors through both the image acquisition process and lens distortion. This study presents a methodology to achieve accurate 2-dimensional (2-D) total length (TL) estimates of fish without specialist equipment or proprietary software. Photographs of fish were captured with an action camera using a background fiducial marker, a foreground fiducial marker and a laser marker. The geometric properties of the lens were modelled with OpenCV to correct image distortion. TL estimates were corrected for parallax effects using an algorithm requiring only the initial length estimate and known fish morphometric relationships. Correcting image distortion decreased RMSE by 96% and the percentage mean bias error (%MBE) by 50%. Correcting for parallax effects achieved a %MBE of −0.6%. This study demonstrates that the morphometric measurement of different species can be accurately estimated without the need for complex camera equipment, making it particularly suitable for deployment in citizen science and other volunteer-based data collection endeavours.

Young-of-the-year (0-group) fish in the Barents Sea have been investigated in an annual joint Norwegian-Russian pelagic trawl survey in autumn, using a standardized procedure since 1980. We use a conceptual framework of ‘upstream’ spawning areas and ‘downstream’ nursery areas, recorded as 0-group distribution in the Barents Sea, to address spatial (geographical) and temporal (1980–2017) variation in 0-group length. Four boreal species (cod Gadus morhua, haddock Melanogrammus aeglefinus, herring Clupea harengus, and deepwater redfish Sebastes mentella) tended to have smaller 0-group individuals in the northern and eastern parts of the Barents Sea, with the largest individuals found in the central part where they were also most abundant. We interpret this to reflect slower growth as the ‘fore-runners’ of the seasonal cohort of juveniles are transported into colder waters (through lateral mixing). The Arctic species (capelin Mallotus villosus and polar cod Boreogadus saida) showed a different pattern with increasing 0-group length with increasing distance away from the spawning areas, seen most clearly for capelin. The longer juveniles in northern areas are probably older and stemming from early spawning.

In the present study, sampling was monthly collected from commercial fishing longline boats operating in the southeastern Mediterranean Sea (Arsuz coast) during September 2017-April 2018 and the relationship between fish length and otolith dimensions (length, width and weight) of 151 redcoat samples were examined. Right otolith pairs were used for calculations since there were no statistical differences between left and right otoliths (P>0.05). Total fish lengths of all samples ranged from between 11.4-21.0 cm. Otolith lengths and otolith widths were calculated between 0.35-0.86 cm and 0.26-0.56 cm for all samples. Otolith weights were determined between 0.010-0.059 g. Total fish length-otolith length, total fish length-otolith width and total fish length-otolith weight relationships were determined as OL= 0.0512TL+0.186 (r2=0.865), OWi= 0.0255TL+0.0021 (r2=0.825) and OW= 0.00002TL2.678 (r2=0.936) on the total of 151 specimens, respectively. Linear relationships between total fish length-otolith length and total fish length-otolith width were found in all fish. The results of study will have new contributions to the field and useful to fisheries management.

The aim of this study was to determine a correlation between the length, width and weight of otoliths and the length and weight of fish samples of Amblypharyngodon mola (Hamilton,1822), a Rasborine fish caught from Middle Ganga region. Total length (TL) measurements were made with a 1mm precision fish length measuring scale. Image J software was used for measuring otolith length and width. This study shows strong correlation between fish length (TL), otolith length (OL) and width (OW), and similarly shows the correlation between Fish weight (TW) with otolith mass (test, P

This study employed underwater cameras and simple spatial mechanism design to capture real-time demersal fish (e.g., Epinephelus lanceolatus or the so-called giant grouper) image stream. Computer vision-based algorithm processes and analyzes the captured image to locate a fish inside a bounding box. Sophisticated shape analysis and machine learning technique were then applied to the bounding box region of image to identify and extract the shape contour of the fishes on the image. Next, this contour was used to obtain the location and length of the fishes in image coordinates. Then, by using the spatial information provided to the system earlier (calibration), the scaling information (mm/pixel) can be used to transform the image length to physical scale. Beside, the fish activity also can be calculated based on the difference between current and previous image frame. The application of the research results can provide information for understanding the growing trend of fishes for fish farmers. In addition, the conversion of fish length and weight and detection of fish activity performed during feeding can serve as critical references for precise feeding management to mitigate feed waste and impede water quality deterioration.