International Journal of Aquatic Biology (2015) 3(4): 258-262 ISSN: 2322-5270; P-ISSN: 2383-0956 Journal homepage: www.NPAJournals.com © 2015 NPAJournals. All rights reserved Short Communication Selected population characteristics of the non-native catfish Hoplosternum littorale (Hancock, 1828) in central Florida, USA Alexander Benjamin Orfinger1 Department of Biology, University of Central Florida, 4000 Central Florida Boulevard, Orlando, Florida 32825, USA. Article history: Received 2 March 2015 Accepted 14 April 2015 Available online 2 5 August 2015 Keywords: Hoplosternum Length-weight relationship Fulton's condition factor Sex ratio Abstract: This study reports the length-weight relationship (LWR), Fulton's condition factor (K), and sex ratio of the non-native catfish Hoplosternum littorale (Hancock, 1828) in Florida for the first time. Sampling was conducted from November 2013 to April 2014 in Tosohatchee Wildlife Management Area in Christmas, Florida. A total of 477 specimens were caught (6.4-13.5 cm TL). The allometric coefficient b of the LWR was greater than the isometric value (b=3.11), suggesting positive allometric growth. The average value for Fulton's condition factor (K) was 1.396, with no significant differences between juvenile and adult size classes. The results present certain disparities from data recorded from the fishes' native range, suggesting that this freshwater invasive may be flourishing in Florida. In addition, a new maximum total length of the species is reported. Introduction In 1995, an established population of Hoplosternum littorale (Hancock, 1828) (Siluriformes, Callichthyi- dae) was detected in the Indian River Lagoon in central Florida (Nico et al., 1996). This Neotropical species is a microphagous scavenger commonly found throughout much of tropical South America and Trinidad (Winemiller, 1987). The species has since spread over much of peninsular Florida, possibly constituting an invasive threat to the freshwater ecosystem (Duxbury et al., 2010) and creating a new small-scale commercial fishery (Gestring et al., 2009). The present work provides the first data on the length-weight relationships (LWR), Fulton's condition factor (K), and sex ratio of this species from Florida. LWRs and Fulton's condition factor are biological parameters commonly used to measure the physiological welfare of fish populations and are an effective means to assess the general productivity of a population (Froese, 2006). * Corresponding author: Alexander B. Orfinger E-mail address: aorfinger@knights.ucf.edu The information herein may be applied for population dynamic models in comparing native and introduced populations as well as population structure across the state of Florida. Materials and Methods From November 2013 to April 2014, the samples were collected from sites throughout Tosohatchee Wildlife Management Area (c. 28°29'56"N, 80°55'1"W), a protected area of the middle St. Johns River Basin spanning 12,424.25 hectares. Sampling efforts focused on Tosohatchee Creek, the St. Johns River, and large ditches connecting the former two water bodies, all rich with various aquatic macrophytes. Fish were captured using a 1.524 m radius cast net with 0.9525 cm nylon mesh. Species identification was confirmed according to Reis (1997). Samples were transported on ice to the laboratory where they were fixed in 10% buffered formalin and counted and measured for total length (TL) and weight (g). Lengths were measured to the 259 Orfinger/ Population characteristics of Hoplosternum littorale nearest 0.1 cm using a digital caliper and weights to the nearest 0.1 g with a digital balance. LWR was calculated using the formula according Le Cren (1951) as follows: W = 𝛼Lb Where, W is the total body weight (g), L is the total length (cm), 𝛼 is the intercept of the regression and b is the regression coefficient (i.e. growth rate). The parameters 𝛼 and b were estimated using the least- square linear regression method (Froese, 2006) after log-transforming the above equation as follows: logW = 𝛼 + b logL The regression coefficient provides information on fish growth. Growth is isometric if b = 3 and allometric if b ≠ 3; negative allometry (fish becomes relatively slender as it grows) is noted if b<3 and positive allometry (fish becomes relatively fatter or deeper-bodied as it grows) is noted if b>3 (Froese, 2006). The 95% confidence intervals for b were calculated to determine if the predicted value of isometry (3.0) fitted between these intervals (Froese, 2006). Fulton's condition factor was derived using the relationship: K = 100W/L3, Where, W = weight of the fish in grams, L = total length of the fish in centimeters, and 3 is the length coefficient to allow the K values to tend towards one. Condition factor was evaluated by size classes (6.0- 9.9 cm and 10.0-13.9 cm) to evaluate physiological differences through ontogeny) and by overall population. Size classes divided juvenile and adult individuals as suggested by Hahn et al. (1997) and Hostache and Mol (1998). Sex ratio was determined from 100 haphazardly subsampled individuals. Those individuals were dissected and their gonads inspected to determine their sex. Results and Discussion A total of 477 H. littorale individuals were caught ranging in size from 6.4-13.5 cm and weight from 3.6-37 g. The results of LWR are summarized in Table 1. The value of b was significantly different than the isometric value of 3 (b = 3.11 ± 0.075, P<0.05, student's t-test) suggesting slight positive allometric growth. The average condition factor for the population was K=1.396 and did not vary significantly between length classes (P<0.05). Finally, of the 100 individuals evaluated for sex, 51 were males and 49 were females, emulating an approximately normal (i.e. 1:1) ratio. The b parameter of the LWR from this study is significantly larger than those provided in former studies (b=2.84 (Oliva-Paterna et al., 2009) and b=2.72 (do Nascimento et al., 2013)). Also, the maximum condition factor calculated by do Nascimento et al. (2013) was significantly lower than in this study (K=1.15 versus K=1.396, respectively; P<0.05). These data suggest that H. littorale populations are obtaining greater relative weights in Florida in comparison to their native range (e.g. Brazil in the case of Oliva-Paterna et al., 2009 and do Nascimento et al., 2013). Such success could be contributed to access to more or novel resources, parasite or predator release, reduced competition than is found in the native range of H. littorale, or a combination thereof. Supporting the above notion, the central Florida population demonstrated a pattern of positive allometric growth whereas the former two studies noted negative allometry. The calculated LWR and condition factor for Florida will be useful for understanding the population dynamics of this invasive fish and further investigations on its growth in the region. The 1:1 sex ratio is congruent with that in wild populations of H. littorale in Trinidad (Singh, 1978), but differs from the ratio (1.2:0.8) noted in northeastern Brazil by do Nascimento et al. (2013). The former study consisted of multi-year field N Total Length (cm) Total Weight (g) Regression Parameters Min Max Min Max log(a) b 95% CI (a) 95% CI (b) r2 477 6.4 13.5 3.6 37 -1.98 3.11 (-2.05)-(-1.90) 3.03-3.19 0.93 Table 1. Minimum and maximum length range, regression parameters, and 95% confidence intervals for Hoplosternum littorale in central Florida. 260 International Journal of Aquatic Biology (2015) 3(4): 258-262 sampling of hundreds of fishes. The 2013 study by do Nascimento et al. (2013) inspected only 70 fishes and was conducted solely during breeding season. This sampling regime may explain the male bias given that males aggressively protect their nests, making them much easier to catch. The present study sampled fish during the entirety of the non- reproductive season for H. littorale in Florida, ensuring that the sex ratio is not biased by guarding males (Nico et al., 2004). As an additional note, while searching for specimens of H. littorale in the University of Central Florida Department of Biology ichthyology collection, the author found two notably large male specimens of 25 cm TL and 26.3 cm TL, respectively. The latter length represents the new maximum length of the species; the former maximum length was 25.4 cm TL as reported by Antonetti et al. (2013). The two specimens noted here were collected in March 2001 in the St. Johns River in central Florida at approximately 29°10'3"N, 81°31'23"W by an unknown collector and are currently stored in 70% ethanol. To date, the LWR, condition factor, and sex ratio of this species have not been reported from Florida. Thus, this work provides the first data available for the region. The population characteristics noted here may be applied in population dynamic modeling to aid in conservation efforts. Likewise, the disparity of LWR and condition factor in native and non-native ranges provide incentive to investigate deeper the mechanisms of success for this species in Florida. Ultimately, the data provided here are a useful metric in measuring the success of a freshwater non-native species in Florida. The baseline information herein could help to influence necessary management strategies of H. littorale in the state. Acknowledgments The author wishes to thank Aileen Perilla for assistance during field work and the personnel of Tosohatchee Wildlife Management Area. Juan Bogota and Julia Behler reviewed the manuscript, providing helpful feedback. References Antonetti D.A., Leal M.E., Schulz U.H. (2014). Length‐ weight relationships for 19 fish species from the Jacuí Delta, RS, Brazil. Journal of Applied Ichthyology, 30: 259-260. do Nascimento Chaves F.D., Sánchez-Botero J.I., Sequeira Garce D., Cavalcanti dos Reis V. (2013). Population features of Hoplosternum littorale (Hancock, 1828) (Siluriformes, Callichthyidae) at Santo Anastacio Reservoir, Brazil. Revista MVZ Córdoba, 18: 3767-3772. Duxbury C., Holland J., Marianne P. (2010). Experimental Evaluation of the Impacts of the Invasive Catfish Hoplosternum littorale (Hancock, 1828) on Aquatic Macroinvertebrates. Aquatic Invasions, 5(1): 97-102. Froese R. (2006). Cube law, condition factor and weight– length relationships: history, meta-analysis and recommendations. Journal of Applied Ichthyology, 22: 241-253. Gestring K.B., Shafland P.L., Stanford, M.S, Eisenhauer R.L. (2009). Status and selected life history attibutes of the illegally introduced brown hoplo (Hoplosternum littorale) in Florida. Florida Scientist, 72: 37-47. Hahn N.S., Almeida V.L.L.D., Luz K.D.G.D. (1997). Feeding and diel cycle of Hoplosternum uttorale (Hancock)(Siluriformes, Callichthyidae) in the lagoons Guaraná and Patos of the upper Paraná river, Brazil. Revista Brasileira de Zoologia, 14(1), 57-64. Hostache G., Mol J.H. (1998). Reproductive biology of the neotropical armoured catfish Hoplosternum littorale (Siluriformes-Callichthyidae): a synthesis stressing the role of the floating bubble nest. Aquatic Living Resources, 11(03): 173-185. Le Cren E.D. (1951). The length-weight relationship and seasonal cycle in gonad weight and condition in the perch (Perca fluviatilis). Journal of Animal Ecology, 20(2): 201-219. Nico L.G., Walsh S.J., Robins R.H. (1996). An introduced population of the South American callichthyid catfish Hoplosternum littorale in the Indian River Lagoon system, Florida. Florida Scientist, 59: 189-200. Nico L.G., Muench A.M. (2004). Nests and nest habitats of the invasive catfish Hoplosternum littorale in lake Tohopekaliga, Florida: a novel association with non- native Hydrilla verticillata. Southeastern Naturalist, 261 Orfinger/ Population characteristics of Hoplosternum littorale 3(3): 451-466. Oliva-Paterna F.J., Torralva M., Carvalho E.D. (2009). Length-weight relationship for 20 species collected in the Jurumirim reservoir (Paranapanema Basin, Brazil). Journal of Applied Ichthyology, 25: 360-361. Reis, R.E. (1997). Revision of the neotropical catfish genus Hoplosternum (Ostariophysi: Siluriformes: Callichthyidae), with the description of two new genera and three new species. Ichthyological Exploration of Freshwaters, 7: 299-326. Singh T.B. (1978). The biology of the Cascadura, Hoplosternum littorale with reference to its reproductive biology and population dynamics. Ph.D. Thesis. University of West Indies, St.-Augustine, Trinidad, 298 p. Winemiller K.O. (1987). Feeding and reproductive biology of the currito, Hoplosternum littorale, in the Venezuelan llanos with comments on the possible function of the enlarged male pectoral spines. Environmental Biology of Fishes, 20(3): 219-227. International Journal of Aquatic Biology (2015) 3(4): 258-262 ISSN: 2322-5270; P-ISSN: 2383-0956 Journal homepage: www.NPAJournals.com © 2015 NPAJournals. All rights reserved چکیده فارسی از فلوریدا Hoplosternum littorale (Hancock, 1828) بومیماهی غیرهای جمعیت انتخاب شده گربهویژگی مرکزی، ایالت متحده آمریکا اورفینگر نجامینب الکساندر .آمریکا متحده ایالت فلوریدا،، 0444دانشگاه مرکزی فلوریدا، بلوار مرکزی فلوریدا ،شناسیزیست گروه چکیده: Hoplosternum littorale( و نسبت جنسی گربه ماهی غیر بومی Kفاکتور وضعیت فولتون ) ،(LWRوزن )-این مطالعه رابطه طول (Hancock, 1828) ناحیه مدیریت در 3400الی آوریل 3402از نوامبر سال برداری. نمونهدکنبرای اولین بار گزارش می آمریکا را در فلوریدا . ندمتر صید شدیتسان 0/6-5/02نمونه با دامنه طول کل 044در کریسمس فلوریدا انجام شد. در مجموع Tosohatchee حیات وحش ( که بیانگر الگوی رشد آلومتریک مثبت b=00/2ار برای رشد ایزومتریک بود )انتظوزن بیشتر از مقدار مورد -ه طولطراب b تریکمضریب آلو های طولی نوجوان و بالغ وجود نداشت. داری بین کالسبود و تفاوت معنی 296/0( Kوضعیت فولتون ) باشد. مقدار میانگین فاکتورمیاین گونه اشد که تواند بدر محدوده بومی پراکنش آن نشان داد که بیانگر این موضوع می های ثبت شده این گونهاختالف بارزی را نسبت به دادهنتایج عالوه یک ثبت جدید از حداکثر طول کل این گونه نیز در این مطالعه گزارش . بهاستاین گونه مهاجم آب شیرین در حال گسترش در فلوریدا شود.می .نسبت جنسی، فاکتور وضعیت فولتون، وزن-رابطه طول، Hoplosternum:کلمات کلیدی