Monday, August 13, 2018

Sunfishes (Lepomis) of Virginia, by Don Orth

Centrarchid fishes exist only in North American freshwaters and are well known as popular sport and aquarium fishes.  There are 38 species in eight genera, all of which may be identified by a laterally compressed body, two connected spiny and soft dorsal fins, spines on anal fins, and pelvic fins in a thoracic position.  The most diverse genus is Lepomis, commonly referred to as the sunfishes in recognition of their highly colored breeding colors.  These colorful sunfish are often the first fish caught and remembered by a young angler.  Their importance in sustaining American sport fisheries cannot be overstated.    Virginia has eight species of Lepomis, but there are thirteen in North America (Warren 2009).  Explore this link to a gallery of photos of Lepomis.  

Due to the popularity as a sport fish, sunfish are widely introduced throughout North America and even in other continents.  The body form and habits all support a generalized sight-feeding habit on a variety of crustaceans, insects, and small fishes. Males develop bright breeding coloration, establish territories, and build shallow, circular nests. Nests may be solitary or colonial and males aggressively defend their nest, court females, and guard eggs and young.  Closely related species have a tendency to hybridize, complicating the identification.  Because of the high fecundity and parental guarding behavior, many young sunfish are produced and become prey for numerous sport fish and other aquatic predators, such as water snakes Nerodia, snapping turtles Chelydra serpentina, and hellbenders Cryptobranchus alleganiensis
Male sunfish guarding a circular, depression nest.  Photo by Alan Creech.  Creative Commons
The male nest construction and guarding and courting behaviors are well studied and all species of Lepomis demonstrate similarities in breeding.  The breeding male excavates a circular depression and defends the territory against all intruders.  This is a great time to get up close and personal with a male sunfish because they are so reluctant to flee.  See this photo of a beautiful male sunfish made possible because it was defending a nest.  During nest defense, the male sunfish displays to nearby or approaching males and females with a behavioral repertoire that consists of  nest hovering, dashes to the water surface and back to the nest, nest sweeping with caudal fin, fin spreading, mouth gapes, jaw snaps, lateral displays, substrate biting, and opercular spreads.  Rim circling behaviors where the male rapidly swims around the edge of the nest with fins erect are intended to attract a female. Opercular flaring is directed at females and apparently signals to the female the species, condition, and quality of the breeding male.  Males also use sounds to court mates.  If the female follows, the male performs courtship circles, encircling the female and leading her to the nest. The size of the male earflap is a key determinant of dominance in a hierarchy. 

Here are the eight species of sunfishes of Virginia.  

Redbreast Sunfish Lepomis auritus is native to the Atlantic slope drainages of Virginia but is now well established in all Virginia waters, except some acidic swampy drainages.  This sunfish has a moderate size mouth  with the upper jaw extending to the anterior edge of the eye.  Body is olive on the back and sides with yellow orange spots on the side and an orange breast.  Iridescent blue wavy lines radiate from the mouth across the snout and onto the cheek and opercle.   The ear flap is narrow and elongate, dark to the posterior margin. 
Redbreast Sunfish Lepomis auritus. Photo by Noel Burkhead.  Source
Green Sunfish Lepomis cyanellus is a very common and spunky sunfish that may occur in streams, rivers, ponds, and shallow weedy margins of lakes. The body shape is not as deep and the mouth is large. The coloration is blue green on back and sides with reflections of yellow and emerald.  The cheeks have distinctive blue wavy streaks.  The ear flap is black with white or yellow orange margins and is not elongated or flexible as in some other sunfish.  Black blotches are usually present near the base of soft dorsal and anal fins.  The pectoral fin is rounded and, when bent forward, will not extend beyond the front of the eye.  The fringe of white, yellow and/or orange along the fins develops in breeding males.   
Green Sunfish Lepomis cyanellus.  Photo by Nate Tessler
Pumpkinseed Lepomis gibbosus seem to prefer vegetated streams, ponds, and reservoirs.  Pumpkinseeds have wavy blue lines on the cheek and opercle.  The opercular flap is short and stiff with a black center, bordered by a semicircular spot on the posterior edge.  This spot may be white, pale yellow, or red.  The pectoral fin is long, and sharply pointed. When bent forward, the pectoral fin will reach beyond the front of the eye.  Pumpkinseed have specialized molariform teeth in their throat, used for crushing snail shells.  
Pumpkinseed Lepomis gibbosus.  Photo by Olaf Nelson.  Creative Commons
Warmouth Lepomis gulosus occur in vegetated lakes, ponds, swamps, reservoirs, and sluggish habitats in streams.  Warmouth has a large, terminal oblique mouth with lower jaw projecting slightly past the upper jaw.  Three to five dark red bands radiate from the snout.  The opercular flap is short and stiff, and black with paler often red-tinged border.  The coloration is olive brown with dark brown mottling on back and side and dark spots and bands on fins.  The pectoral fin is short and round, usually not reaching the eye when laid forward.  Breeding males (pictured below) are boldly patterned with a red orange spot at the base of the second dorsal fin and black pelvic fins.  
Warmouth Lepomis gulosus.   Photo by Olaf Nelson.  Creative Commons
Bluegill Sunfish Lepomis macrochirus occupy all types of lacustrine and fluvial habitats.  Bluegill have a small mouth.   They have a large black spot at posterior end of soft dorsal fin.   Opercular flap is moderate or long and flexible with black margins. Coloration is blue with dark chain-like bars along the side, which may be absent.  Adults will have two blue streaks from the chin to the edge of the gill cover.   Pectoral fin is long and pointed.     
Bluegill from Lake Lanier, Georgia.  Creative Commons
Hybrid Bream -- The hybrid between the Bluegill Sunfish and the Green Sunfish is commonly produced and marketed for stocking in farm ponds.  The F1 has desirable traits such as enhanced growth and reduced fertility.  The photo below is a hybrid that has blue cheek lines of the Green Sunfish and chain-like bars of the Bluegill. 
Hybrid Bream.  Photo by MSU Extension Service/Wes Neal
Dollar Sunfish Lepomis marginatus occur only below the fall line and inhabit swamp-like habitats in low gradient streams and beaver ponds.  They are the smallest Lepomis in Virginia, and max out at only 4 inches.  The mouth is small and there are wavy blue lines on cheek and opercle.  The opercular flap is long, flexible, black in the center and edged with lighter margins.  Coloration is dark red on back and bright orange on the belly with many blue spots on the side.    
Dollar Sunfish Lepomis marginatus  Photo by Derek Wheaton
Longear Sunfish Lepomis megalotis  inhabits pools of headwaters, creeks, and small to medium sized rivers.  Longear Sunfish have distinctive wavy blue lines on snout, cheek, and opercle.  The opercular flap is long and flexible with a black center and shite edges of equal with.  the pectoral fin is short and rounded, not reaching the eye when laid forward.   Adults are dark red above, bright orange below, and marbled and spotted with blue on the side.  Longear Sunfish vigorously attach a variety of baits and is frequently caught with spin and fly fishing.  
Longear Sunfish  Lepomis megalotis.  Photo by Brett Albanese, Georgia DNR
Redear Sunfish Lepomis microlophus inhabits ponds lakes and reservoirs and sluggish pools and backwaters of rivers. Redear Sunfish resemble Bluegill. They do not have wavy blue lines on the head.  The opercular flap is short, with black center  and bordered above and below in white margins and posteriorly with a prominent red or orange crescent.  Coloration is light gold green above with many dark connected spots on the side.  Pectoral fin is long and pointed.     It is widely stocked for sport fishing and eats snails and small bivalves, earning it the name "shellcracker."  Anglers catch Redear Sunfish with worms and other natural baits fished near the bottom.  
Redear Sunfish  Lepomis microlophus.  Photo by Kentucky Dept. of Fish & Wildlife Resources.
The fascinating sunfishes Lepomis spp. are North American treasures.   They are easy to catch, fun to watch, good to eat, and provide many opportunities for education and scientific study.   In addition to the Lepomis spp., other centrarchid fishes include the include Mud Sunfish (Acantharchus pomotis), Flier (Centrarchus macropterus), two rock basses (Ambloplites), three banded sunfishes (Enneacanthus), two crappies (Pomoxis),  and three black basses (Micropterus).    

Catching sunfish makes young ones happy.  Photo by Joseph Bartmann.  Creative Commons


Warren Jr., M.L., 2009.  Centrarchid identification and natural history.  Pages 375-533 in S.J. Cooke and D.P. Philipp, editors. Centrarchid fishes: Diversity, Biology, and Conservation.  Blackwell Publishing, Ltd., United Kingdom.

Friday, August 3, 2018

Eye Picking and Pebble Picking Behaviors of Cutlip Minnow, by Don Orth

Cutlip Minnow Exoglossum maxillingua is no ordinary minnow.  Two behaviors make it quite unique -- nest building and eye picking. Compared to other minnows, its movements are sluggish, staying near the bottom of clear, rocky streams. But during the spring breeding season, males become hard-working nest builders, selecting pebbles and bringing them to the nest site at a rate up to 6-10 per minute.  This eventually results in a pebble mound that can be 12 to 18 inches across and 5 to 6 inches high.   Wow!  Just consider the energy expended by nest building and tending – a 6-inch Cutlip Minnow can barely transfer a ¾ inch pebble.  Females are smaller and do not participate in the nest building.  The male stays at the nest day and night until breeding has ceased (Hankinson 1922; van Duzer 1939). 

Cutlip Minnow.  Photo by Matt Tillet

The distribution of the Cutlip Minnow ranges from Virginia to New York in streams of the mountains and piedmont provinces.   Here, the Cutlip Minnow co-occurs with many other fishes, including the Common Shiner Luxilus cornutus, Creek Chub Semotilus atromaculatus, Rosyface Shiner Notropis rubellus,  Tesselated Darter Etheostoma olmstedi, White Sucker Catostomus commersoni, and Blacknose Dace Rhinichthys atratulus.   Common Shiner and Rosyface Shiner breed on the nests built by Cutlip Minnows and their constant swimming and darting is in contrast to the behavior of the Cutlip Minnow (van Duzer 1939; Maraukis et al. 1991).  

Distribution of the Cutlip Minnow from NatureServe.

The eye-picking behavior of the Cutlip Minnows has frustrated many field biologists when collecting these fishes.  All types of fishes collected are typically placed in a large bucket until enough are collected to identify and count them all.  Collected fishes held in the bucket with the Cutlip Minnows often have missing or damaged eyes.  Antonios Pappantoniou and George Dale  (1986) discovered that the Cutlip Minnow would immediately pick at the eyes of a goldfish added to an aquarium with many Cutlip minnows.   Furthermore, the Cutlip Minnows were not fooled by the camouflage of  false eyespots or eye lines on fishes (Dale and Pappantoniou 1986).  When in crowded situations, the Cutlip Minnows like fish eyes!

Close-up, ventral view of the mouth of the Cutlip Minnow.  Photo by Brian Zimmerman.
The mouth of the Cutlip Minnow is unique in that the lower jaw consists of a central bony plate flanked by two fleshy lobes.  Only one other fish, the Tonguetied Minnow Exoglossum laurae, has this unique mouth morphology   The ventral mouth would seem to be specialized adaptation for benthic feeding on snails, insect larvae, and diatoms.  Eye-picking does not appear to be an adaptation for feeding on the eyes of other fishes.  The mouth morphology also facilitates the transport of pebbles of a particular size as seen in other nest building cyprinids (Bolton et al. 2015).

In a recent study, Bramburger et al. (2018) observed that nests of Cutlip Minnow were composed of mainly dark pigmented pebbles.  They speculated that the colorful, dark pebble might enhance mate selection by female Cutlip Minnows. Male Cutlip Minnows get darker during breeding but they do not possess secondary sexual characteristics that would serve as cues for sexual selection.   However, Bramburger et al. discovered that the substrate from nests were significantly darker and more saturated than random samples of stream substrata.  No other examples of nest substratum color selectivity has been reported in fishes.  At this stage, all one can do is speculate.   Perhaps darker substrate absorbs/conducts more heat energy (Brown 1969; Johnson 2004) that speeds embryo development.

Our not so ordinary little minnow may possess secrets that are yet to be explained.  

Bolton, C., B.K. Peoples, and E.A. Frimpong. 2015. Recognizing gape limitation and interannual variability in bluehead chub nesting microhabitat use in a small Virginia stream. Journal of Freshwater Ecology 30: 503-511.  
Bramburger, A. J., K.E. Moir, and M.B.C. Hickey. 2018. Preferential incorporation of dark, coloured materials into nests by a mound-nesting stream cyprinid. Journal of Fish Biology
Brown, G. W. 1969. Predicting temperatures of small streams. Water Resources Research 5:68-75. 
Dale, G. and A. Pappantoniou. 1986.  Eye picking behavior of the cutlips minnow, Exoglossum maxillingua:  Applications to studies of eye spot mimicry.  Annals of the New York Academy of Science 463:177-178.
Hankinson, T.L. 1922.  Nest of cut-lips minnow, Exoglossum maxillingua (LeSueur). Copeia 102:1-3.
Johnson, S. L. 2004. Factors influencing stream temperatures in small streams: substrate effects and a shading experiment. Canadian Journal of Fisheries and Aquatic Sciences 61(6):913-923.
Maurakis, E.G., W.S. Woolcott, and M.H. Sabaj. 1991. Reproductive behavior of Exoglossum species. Bulletin of the Alabama Museum of Natural History 10:11-16.
Pappantoniou, A., and G. Dale.  1986.  Eye-picking behavior of the cutlips minnow Exoglossum maxillingua: density relationships.   Annals of the New York Academy of Sciences. 463:206-208.
van Duzer, E.M. (1939) Observations on the Breeding Habits of the Cut-Lips Minnow, Exoglossum maxillingua. Copeia  1939:65-75.