Carapace Length Research Articles

Cherax quadricarinatus: Identifying potentially invasive species in Lake Laut Tawar through their bio-population aspects

Cherax quadricarinatus is an introduced species that is deliberately stocked in Lake Laut Tawar, Takengon, Indonesia. This study aims to analyze bio-population aspect of this species, including length frequency distribution, length-weight relationship, condition factors, and biology reproductive. A total of 361 individual was sampled bi-weekly from October to December 2021 in Lake Laut Tawar, Central Aceh, Indonesia. The carapace length of the crayfish ranged from 26.5 to 69.9 mm CL, with the length class mode being 41.69 mm CL. The growth pattern of freshwater crayfish is negative allometric (b<3) as described as an equation W = 0.0002CL29522 (R2 = 0.907). The sex ratio of C. quadricarinatus between male and female was in balance ratio (1:1) (Chi-square test result). The length of maturity (L 50) in male was 49.49 mm CL, while in female was 47.41 mm CL. The highest gonad somatic index (GSI) was in December at 1.02, while the lowest was in November at 0.79. Fecundity of female ranged from 267 to 970 eggs.

Diet of hawksbill turtles (Eretmochelys imbricata) in the Gulf of California, Mexico

Abstract Hawksbill turtles (n = 56) in a foraging ground around Isla San Jose, Gulf of California, Mexico, were caught, measured, and their skin and scutes sampled. Tissue samples from putative prey species were collected from observed hawksbill feeding areas in the foraging ground. Measurements of each turtle's straight carapace length were used to estimate the average life stage of the population. Tissue samples were processed for stable carbon and nitrogen isotope analysis to estimate foraging habits of turtles in this location. The majority (96.4%) of measured individuals' straight carapace length fell in the size range considered to be juveniles. A Bayesian mixing model analysis of the δ13C and δ15N values of hawksbill skin and potential prey indicated that hawksbills consume primarily invertebrates and algae, with lesser contributions from seagrass and mangrove material. There was a positive linear relationship between turtle size and the δ13C values from scute samples, and an increase in the δ13C values of five individuals recaptured in subsequent years suggested a potential location shift from a pelagic habitat in the turtles' post‐hatching, earliest juvenile years to the nearshore foraging area around Isla San Jose in their later juvenile years.

Limited holding space reduces growth and behavioural performance in juvenile European lobsters

Conservation aquaculture offers important tools to secure sustainable animal supplies for human use. However, intensive aquaculture practices are increasingly raising concerns about the welfare conditions of farmed animals, which typically face high mortality rates due to diseases, cannibalism, and aggression. Here we focus on the European lobster (Homarus gammarus), an economically and ecologically important decapod species that has been subjected to conservation programs for decades. While standard husbandry procedures typically result into large numbers of juvenile lobsters produced and released, it remains poorly known whether such standard settings alter the development of behavioural and life-history traits of ecological importance for the animals to survive in the wild. Here, we investigate whether the size of the individual holding spaces affects the behavioural traits (exploration, space use, and sheltering) and growth (carapace length, intermoult period, and percentage moult increment) of juvenile lobsters during their early benthic stages. Our results offer solid evidence that rearing lobsters into small holding spaces not only limits and slows down their overall growth, but also compromises the development of ecologically-relevant behaviours that are essentials for these animals to survive in a complex and risky environment. We point the attention toward the benefits of adopting better rearing procedures to improve the welfare conditions of hatchery-cultured lobsters that can, in turn, result into faster growth rates and the development of competent behavioural repertoires of these valuable organisms—likely to improve the effectiveness of conservation programs.

Morphometric Study of African Spurred Tortoise (Centrochelys sulcata) Based on Age Group

Centrochelys sulcata are kept and bred to prevent extinction. The sulkata tortoises were identified to determine their respective identities by measuring them morphometrically. Morphometric studies on sulkata tortoises are still minimal, so a morphometric study of the sulkata tortoises is needed. The purpose of this study was to identify and describe the morphometry of sulcata tortoises with three different age ranges kept in ex-situ conservation. The research sample used 15 sulcata turtles which were divided into 3 groups namely group A (1 year), Group B (2 years), and Group C (3 years). The morphometric parameters measured were body weight, head, carapace, plastron, forelimb, hindlimb and bridge. The results showed that the average body weight of group A, B and C turtles was 2,179 kg, 1,289 kg and 0,167 kg respectively. The average maximum carapace length in a row for groups A, B, C, namely 11.64, 23.18 and 16.72 cm. The average plastron lengths for groups A, B, C were 9.08, 6.44 and 9.24 cm respectively. The average forelimb length in groups A, B and C were 3.04, 6.28 and 7.78 cm respectively. The average hindlimb length for groups A, B, and C were 1.86, 3.5 and 4.04 cm, respectively. The average bridge width for groups A, B and C were 4.36, 8.94 and 10.1 cm respectively. Based on the results of morphometric measurements of the three groups of sulcata tortoises, it was shown that group C had a larger morphometric size than groups B and A, this was due to differences in age and growth factors. Sulcata tortoises group C is 3 years old and belongs to the juvenile group. Sulcata tortoise groups A and B aged 1 and 2 years are included in the yearly group

Satellite tracking reveals use of Biscayne National Park by sea turtles tagged in multiple locations

Although historical observations date back to the 1800’s, there is little information on sea turtle occupancy within Biscayne National Park (BNP). The park is located along the Florida reef tract and is dominated by the Gulfstream, which acts as a corridor for many marine animals. Here we used satellite telemetry to determine areas of use in BNP for two species of imperiled sea turtles, loggerhead (Caretta caretta) and green (Chelonia mydas) turtles. We included data for turtles tagged between 2009–2021 at sites both within park waters and in five locations outside the park boundary; individuals were captured both in the water and on land. We tagged 60 individuals (female, n = 48; male, n = 3; immature, n = 9); loggerheads (n = 33) ranged in size from 66.2 to 109.9 cm CCL (curved carapace length) and green turtles (n = 27) ranged in size from 39.1 to 111.9 cm CCL. We used behavioral switching state-space modeling (SSM) to obtain daily predicted positions for each turtle, classified turtle behavior within the park as either foraging, migration, or both foraging and migration, and summarized high-use areas for each species across all months of the year. Turtles used park waters year-round, with concentrated use of deeper waters during seasonal migrations. Across all 60 turtles, 21 spent their tracking time foraging within BNP boundaries and 30 used the park as part of their migratory pathway; five turtles used the park for both foraging and migration, and the remaining four had SSM points very close to the park. Loggerhead migration occurred from February through November, whereas green turtle migration was concentrated in August. Both turtle species exhibited high overlap (i.e., usage) with seagrass habitat. These findings are relevant as managers consider strategies to minimize anthropogenic impacts to resident and migratory sea turtles using park waters.

Development and evaluation of a medium-free incubation method for hatching Chinese soft-shelled turtle (Pelodiscus sinensis) eggs

In aquaculture, the traditional method for hatching Pelodiscus sinensis eggs needs further investigation. Here, we developed a medium-free incubation method for hatching P. sinensis eggs and evaluated its differences from the traditional vermiculite incubation method and the effects of light on it. We found that medium-free incubation had no significant effects on hatching success, body weight, carapace length, carapace width, plastron length, plastron width, and righting response time of P. sinensis compared with those under traditional vermiculite incubation, irrespective of thermostatic or fluctuating temperature conditions. Furthermore, light treatment significantly shortened the incubation period and negatively affected body weight, carapace length, carapace width, plastron length, and righting response time during medium-free incubation. Additionally, this study is the first to report the phenomenon of egg-hatching synchrony in P. sinensis. Overall, our results provide basic data and novel insights for improving the method for hatching P. sinensis eggs.

Origins of green turtle fishery bycatch in the central pacific revealed by mixed genetic markers

Longline fishing vessels, such as those that target tuna or billfish, also unintentionally catch endangered marine turtle species on the high seas. The stock composition of this bycatch is often unknown but potentially complex, with individuals coming from many possible origins on an ocean-basin scale. To better understand the stock composition of green turtle (Chelonia mydas) bycatch we obtained 46 turtles, 27-91 cm in curved carapace length, caught by Hawaii- and American Samoa-based pelagic longline fishing vessels across large areas of the North- and South-central Pacific. We genotyped these at nine microsatellite loci and one mitochondrial DNA marker, and used a baseline of 1,043 nesting female green turtles from beaches across the Pacific for population assignment and mixed-stock analysis. By analyzing both marker types jointly we were able to increase power and genetically resolve ten baseline stocks of nesting females with mean self-assignment and simulated accuracies of 75-97%. Above the Equator, green turtle bycatch was composed mostly of individuals from Hawaiian and Eastern Pacific stocks, with a small number from the Western Pacific. Below the Equator, the most common stocks in the bycatch were from Australia and the Coral Sea, American Samoa and French Polynesia, and the Galápagos Islands. Overall, turtles originating from East, West, and Central Pacific breeding populations were major components of the bycatch, suggesting that the geographic ranges of these populations overlap across large tracts of ocean during the pelagic life history stages.

Studi Morfometrik Kepiting Rajungan (Portunus Pelagicus)

This study aims to reveal the morphometric characteristics crab P. pelagicus in the Sei Berombang estuary waters. The purposive sampling method used to determining 3 sampling stations, sampling process was using trawl nets. The results showed that the P. pelagicus population at Station 1 dominated by small carapace, at stations 2 and 3 found the domination of larger size with juvenile and adult phases category. The morphometric characters of carapace width (CW) in blue/flower crabs ranged from 9.50 to 17.40 cm, left posterolateral carapace length (LPCL) ranged from 2.20-6.70 cm, left anterolateral carapace length (LACL) ranged from 1.30-6.50 cm, right anterolateral carapace length (RACL) ranged from 1.20-7.00 cm, frontal right width (FRMW) ranged from 1.50-3.70 cm, carapace length (CH) ranged from 3.70-7.00 cm, internal carapace width (ICW) ranged from 6, 30-14.10 cm, right orbit (eye socket) width (ROW) ranged from 1.06-2.00 cm, left orbit (eye cavity) width (LOW) ranged from 1.12-2.10 cm, carapace width (CW) ranged from 9.50-17.40 cm, left posterolateral carapace length (LPCL) ranged from 2.20-6.70 cm, and left anterolateral carapace length (LACL) ranged from 1.30-6.50 cm. Conclusion, The morphometric characters of male and female P. pelagicus in the Sei Berombang waters were found to vary spatially and temporally.&#x0D; Kata Kunci: Characteristic Morphology, Identification, Morphometric, P. pelagicus

Plastral deossification zones in the Endangered Spiny Hill Turtle Heosemys spinosa (Testudines: Geoemydidae) on Borneo

Studies of the evolution of turtle shell morphology have raised numerous questions. In this study, five adult females and two adult males of the Endangered Spiny Hill Turtle Heosemys spinosa from two localities in western Sarawak in East Malaysia (Borneo) were examined for the presence of plastral deossification zones, reported as indicative of kinesis in earlier studies. A total of 52 (34 females, 18 males) radiographs demonstrated distinct poorly-ossified areas across the hyo-hypoplastral and the hypo-xiphiplastral junctures in females of straight carapace length (SCL) 143.4–211.4 mm. The feature is here interpreted as a permanent plastral hinge, which was not observed in either of the males examined. The smallest female with a weak but discernible line at the contact of these bones had a SCL of 125 mm, suggestive of minimum size of maturity in Heosemys spinosa in this population.

Length-based Stock Assessment for the Data-poor Crayfish Fishery from the Eğirdir Lake, Turkiye

In this study, a stock assessment of the Pontastacus leptodactylus (Eschscholtz, 1823) population in Egirdir Lake where Turkey's most important crayfish production center, was made. The study was carried out between June 2021 and May 2022 in the concept of length-based data-poor fisheries management. TropFishR R package was used in study due to pretty effective in analysing of the length-frequency (LFQ) data. As a result of monthly fishing trials, 14,919 crayfish were caught between 29.92 and 163.38 mm in total length (14.83 – 80.95 mm carapace length). The female-male ratio of the population was found to be 1:1.21. It was determined that growth occurred (+) allometrically in all sexual groups (female, male, female+male). The growth parameters L∞, K and Ф of the P. leptodactylus stock were found to be 86.06-mm, 0.59/year, and 3.64, respectively. The annual rate of total (Z), natural (M) and fishing mortality (F) were estimated to be 3.02, 0.64, and 2.38/ year, respectively. The exploitation rate (E) of the crayfish stock was estimated to be 0.78, Fcurr/Fmax ratio 1.79 and SPR ratio 0.13. In this context, Egirdir Lake P. leptodactylus stock was evaluated as overfished. To ensure the sustainability of the stock of the species in the lake, it is necessary to reduce the mortality rate caused by fishing.

Maximum Body Size of the Suwannee Alligator Snapping Turtle (Macrochelys suwanniensis)

The published literature does not provide a consensus regarding maximum body sizes of North America's largest wild freshwater turtles (genus Macrochelys). The largest known wild M. suwanniensis (Suwannee Alligator Snapping Turtle) currently exists as a curated specimen measuring 713 mm straight-midline carapace length, 801 mm maximum carapace length, 619 mm maximum carapace width, and 236 mm maximum head width. The turtle was never weighed, but we used morphometric data from our studies in the Santa Fe and Suwannee rivers to estimate that it weighed ∼76.4 kg (168 lbs) when captured. Our 95% prediction interval (67.6–86.3 kg [149–190 lbs]) suggests that speculative estimates and anecdotal reports of M. suwanniensis that weigh ≥90 kg (≥200 lbs) are dubious.

Population Dynamics of Jinga Shrimp (Metapenaeus affinis) in Samboja Kuala Waters Kutai Kartanegara Regency

Pink shrimp (Metapenaeus affinis) or Jinga shrimp is one of the species caught in the waters off Samboja Kuala. This catch is a valuable commodity in the market. The possibility of exploiting shrimp resources will be jeopardized in an effort to conserve, utilize, and catch high intensity shrimp. This study was conducted from September to December 2022 with the aim of determining population dynamics parameters using the frequency method from carapace length data. A mini trawl was used to collect shrimp in the waters of Samboja Kuala, Kutai Kartanegara Regency. Male and female jinga shrimp have a ratio of 1:2,43. Furthermore, for male and female shrimp, the growth rate coefficient (K) was 0,580 and 14,00, respectively, and the approximated natural length (L) was 145.82 and 160.81. Pink shrimp (Metapenaeus affinis) have natural mortality (M) of 1,113/year, mortality due to capture (F) of 0,516, and total mortality (Z) of 1,630, with exploitation value (E) of 0,316, indicating that they are still at the appropriate level. Herefore, female shrimp peaked in August at 14,6% and males peaked in July 31,81%. The Y/R capability was 0,049/year, and Emax calculated the Y/R relationship with the exploitation rate, which was 0,42.

Distribution and Status of the Alligator Snapping Turtle (Macrochelys temminckii) in Alabama

Macrochelys temminckii (Alligator Snapping Turtle) has experienced historical harvesting pressures that impact a number of current populations. Filling distribution gaps and obtaining demographic data can better inform conservation and management. We summarized multi-year samples targeting the Alligator Snapping Turtle in large river systems and major tributaries of Alabama. Although catch per unit effort was lower than observed in other states, we filled distribution gaps in several river systems. Though studies from other states documented effects of historical harvesting pressure on Alligator Snapping Turtle populations, mean adult mass of both sexes, mean carapace length, and capture ratio of adults to immatures suggested reduced pressures in Alabama and possible population stability. Nevertheless, smaller tributaries and creeks need to be surveyed for previously undetected populations with mark–recapture and movement studies.

Determining Sexual Size Dimorphism in an Alligator Snapping Turtle (Macrochelys temminckii) Population in Southwest Georgia: Use of Morphometrics, Ultrasonography, and Testosterone

We studied the determination of sex for intermediate size classes and adult sexual dimorphism in a Georgia population of Macrochelys temminckii (Alligator Snapping Turtle). We sexed turtles when possible based on size and morphometrics. We took blood samples from captured individuals and measured plasma testosterone using enzyme-linked immunoassay. We examined females and individuals for which sex was unknown using ultrasound to determine sex and reproductive status. We used testosterone concentration to confirm individual sex assignments. For all biometric measurements, adult males were larger than females. Testosterone concentrations were higher in adult and subadult males than in females. Head width did not differ between the sexes when adjusted for body size. Plastron-to-vent length (cm) and testosterone concentrations were significantly greater in adult and subadult male turtles compared to females and were valuable in determining sex of smaller adults >25 cm straight-midline carapace length.

A new species of Nanhsiungchelys (Testudines: Cryptodira: Nanhsiungchelyidae) from the Upper Cretaceous of Nanxiong Basin, China.

Nanhsiungchelyidae are a group of large turtles that lived in Asia and North America during the Cretaceous. Here we report a new species of nanhsiungchelyid, Nanhsiungchelys yangi sp. nov., from the Upper Cretaceous of Nanxiong Basin, China. The specimen consists of a well-preserved skull and lower jaw, as well as the anterior parts of the carapace and plastron. The diagnostic features of Nanhsiungchelys include a large entire carapace length (∼55.5 cm), a network of sculptures consisting of pits and ridges on the surface of the skull and shell, shallow cheek emargination and temporal emargination, deep nuchal emargination, and a pair of anterolateral processes on the carapace. However, Nanhsiungchelys yangi differs from the other species of Nanhsiungchelys mainly in having a triangular-shaped snout (in dorsal view) and wide anterolateral processes on the carapace. Additionally, some other characteristics (e.g., the premaxilla is higher than wide, the maxilla is unseen in dorsal views, a small portion of the maxilla extends posterior and ventral of the orbit, and the parietal is bigger than the frontal) are strong evidence to distinguish Nanhsiungchelys yangi from Nanhsiungchelys wuchingensis. A phylogenetic analysis of nanhsiungchelyids places Nanhsiungchelys yangi and Nanhsiungchelys wuchingensis as sister taxa. Nanhsiungchelys yangi and some other nanhsiungchelyids bear distinct anterolateral processes on the carapace, which have not been reported in any extant turtles and may have played a role in protecting the head. The Nanxiong Basin was extremely hot during the Late Cretaceous, and so we suggest that nanhsiungchelyids might have immersed themselves in mud or water to avoid the heat, similar to some extant tortoises. If they were capable of swimming, our computer simulations of fluid flow suggest the anterolateral processes could have reduced drag during locomotion.

Distribution, habitat and population structure of the threatened Manning River helmeted turtle, Myuchelys purvisi

AbstractMany freshwater turtle species are threatened with extinction, but the implementation of effective conservation measures may be hindered by ignorance of their biology and ecology. We analysed the available monitoring data for a listed Endangered but poorly known species, the Manning River helmeted turtle (Myuchelys purvisi: Chelidae), to elucidate its geographic distribution and evaluate its relationships to broad‐scale environmental factors. We found M. purvisi to be common and widely distributed in the Manning River system, with a balanced population structure including a wide mix of size classes and a substantial juvenile component. The occurrence of the species was significantly positively associated with a larger stream size, which probably confers greater habitat availability and lower vulnerability to drying during drought. Mean carapace length was significantly lower in stream segments with higher average annual air temperature, suggesting that warmer conditions favour recruitment. However, occurrence and mean carapace length were not related to the proportion of conservation land in the immediate stream environs, suggesting that persistence of the species is not favoured simply by occurrence in protected areas, and threats may need active management. We provide some suggestions for further investigation of the species' ecology and vulnerability to potential threats.

New Distributional Record of Red Frog Crab, Ranina ranina (Linnaeus, 1758) (Decapoda: Raninidae) with Finding of Maximum Carapace Length from North-West Coast of India

New Distributional Record of Red Frog Crab, Ranina ranina (Linnaeus, 1758) (Decapoda: Raninidae) with Finding of Maximum Carapace Length from North-West Coast of India

Morphological Diversity of Different Male Morphotypes of Giant Freshwater Prawn Macrobrachium rosenbergii (De Man, 1879)

The giant freshwater prawn (GFP), Macrobrachium rosenbergii, is one of the largest palaemonids in the world, found in tropical marine, estuarine, and freshwaters, and is among the most commercially cultured crustaceans. According to research, mature males usually develop differences in cheliped morphology, growth characteristics, and agonistic behavior. The identification of such morphotypes is critical for effectively managing and handling prawns. The present study aimed to describe the GFP male population structure in culture ponds (the Yangtze River delta, China). Sixteen morphometric traits and four weight data were measured for each four male morphotype. Principal component and clustering analyses were conducted to investigate the morphological variation among the four morphotypes. The study of relative growth was also employed to estimate the growth patterns of body structures (dependent variables) in relation to the carapace length (independent variable). A detailed description of the cheliped’s macroscopic characteristics that differed among morphotypes was provided, which corroborated with previous studies of the species. The four morphotypes were statistically different regarding the cheliped morphology, size, and morphometric relationships and equations, indicating a considerable variation in growth among the four male morphotypes. The present results contribute to a clear understanding of the population biology of GFP and support future management and broodstock selection activities.

Plankton depletion by mussel grazing negatively impacts the fitness of lobster larvae

Bivalve aquaculture has rapidly expanded in shallow coastal habitats, leading to substantial changes in the natural environment. While the grazing pressure of mussels (Mytilus edulis) on phytoplankton and zooplankton has been well documented, cascading effects of plankton depletion on the development and survival of resident fish and invertebrate larvae remains largely unexplored. This study experimentally assessed the impact of control (no mussel grazing), low (20 mussels·m−3) and high (80 mussels·m−3) mussel densities on a model community composed of various phytoplankton and zooplankton and how changes in plankton characteristics influence the development and survival of lobster (Homarus americanus) larvae. Mussels fed primarily on nanophytoplankton, while the picophytoplankton experienced significantly less grazing. Zooplankton was readily ingested by mussels, showing a sharp decline under low mussel density, whereas it was eliminated from the plankton under high density of mussels. A 65% decrease of polyunsaturated fatty acids (∑ PUFA) was observed in the plankton under mussel filtration compared to control. Lobster larvae reared under control plankton conditions exhibited the fastest development, highest survival rate, carapace length, total lipid and ∑ PUFA contents, and TAG/ST (triacylglycerols/sterols) ratio, indicating the best nutritional condition. Larvae reared under low mussel density showed longer developmental time, lower survival rate and carapace length than that for controls. In addition, these larvae showed a significant reduction in total lipid, ∑ PUFA, and TAG/ST, which collectively suggests poor nutritional status due to limited dietary intake. Under high mussel density, larvae did not molt to stage II and died within 14 days, suggesting that the depleted plankton community was unable to sustain physiological requirements for survival and development of the larvae. Overall, mussel grazing altered the meroplankton community structure and its biochemical composition, ultimately impacting the development, survival, and quality of lobster larvae. These findings provide novel information on complex trophic interactions between bivalves and a meroplankton species and adds a new perspective to fuel discussions on energy and nutrient pathways, particularly long-chain PUFA, in ecosystem carrying capacity studies for shellfish aquaculture in shallow coastal habitats.

Evidence of a compensatory response in invasive Rusty Crayfish (Faxonius rusticus) following intensive harvest removal from northern Lake Michigan fish spawning reefs.

The online version contains supplementary material available at 10.1007/s10530-023-03076-6.