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Fishery Bulletin 101(4) 



(Vincent, 1996; Vincent and Perry'^), placing populations 

 around the world under greater pressure. Much of this 

 market demand is met from retention of incidental land- 

 ings in shrimp trawls. Where no market has yet developed, 

 incidentally caught seahorses are discarded and the sur- 

 vival rate for these discarded seahorses is unknown. 



Trade records and anecdotal evidence from other coun- 

 tries indicate that the United States has imported and 

 exported considerable numbers of both live and dried 

 seahorses in recent years (Vincent, 1996; Vincent and 

 Perry^). In Florida, the primary source of live seahorses in 

 the United States (Larkin and Degner, 2001), these fishes 

 ranked as the seventh most economically important orna- 

 mental fish group from 1990 to 1998, and seahorse landings 

 rose 184% during this period, whereas landings of each of 

 the more valuable fish groups declined (Adams et al., 2001). 

 Many seahorses in the United States are probably obtained 

 from bycatch of the shrimp trawl fisheries that operate in 

 known seahorse habitats along the Atlantic coast of the 

 United States. 



Our objective was to document bycatch of the lined sea- 

 horse (Hippocampus erectus) in a live-bait shrimp trawl 

 fishery. This fish is often retained for the aquarium trade. 

 We quantify number, sex, size, and reproductive status of 

 trawl-caught seahorses and examine how these parameters 

 vary temporally and spatially. We also comment on poten- 

 tial conservation concerns resulting from this fishery. 



Materials and methods 



We focused our study on the lined seahorse (Hippocam- 

 pus erectus) because it was caught much more often than 

 its sympatric congenerics in the Gulf of Mexico — the 

 longsnout seahorse (H. reidi) and the dwarf seahorse (H. 

 zosterae). Hippocampus erectus is a large, deep-bodied 

 seahorse (adult height 5.5 to 18.5 cm: Lourie et al., 1999) 

 and has a geographic range that extends from southern 

 Canada to Argentina. Most species of seahorse have short 

 lifespans and low fecundity: Hippocampus erectus lives for 

 about four years (Lourie et al., 1999) and has broods of 

 about 100-1500 young (Teixeira and Musick, 2000). Hip- 

 pocam.pus erectus is found in shallow waters and offshore to 

 depths of over 70 m, primarily in mangroves and seagrass 

 beds (Vari, 1982). Like many other seahorse species, H. 

 erectus is listed as Vulnerable (A2cd) by the International 

 Union for Conservation of Nature and Natural Resources 

 (lUCN, 2002), based on suspected declines resulting from 

 habitat degradation and exploitation. However, as is the 

 case for many small fishes, there is little information 

 known about the biology of H. erectus, and no fishery data 

 exist for it. 



Seahorse bycatch was assessed in the live-bait shrimp 

 trawl fishery operating from Hernando Beach, Florida 

 (Fig. 1). The fishery, using roller beam trawls, targets pink 

 shrimp iPenaeus duorarum) at night in seagrass beds and 

 relocates seasonally in Florida. Hernando Beach was cho- 



'^ Vincent, A. C. J., and A. Perry (eds). 2003. Global trade in 

 seahorses. Manuscript in prep. 



sen as our study site because it is a moderate-size fishing 

 port with 31 licensed trawlers and is active during the 

 summer sampling period. Boats were equipped with trawls 

 that had a slotted roller along the bottom of the frame, and 

 stainless steel finger bars attached vertically, 5 cm apart 

 along the length of the frame, to limit collection of benthic 

 substratum and other debris (Berkeley et al., 1985). Trawls 

 were towed from each side of the vessel in four configura- 

 tions: 1) one trawl per side, each measuring either 3.66 m, 

 4.27 m, or 4.88 m in length, or 2) two trawls per side, each 

 measuring 3.66 m in length. Net mesh sizes were 3.18-3.81 

 cm and the tail bag stretched mesh size was 2.54-3.18 cm. 

 Trawls usually lasted between 30 and 60 minutes, and fish- 

 ermen made multiple successive trawls in a night. Shrimp 

 were culled from the catch and held live onboard in aerated 

 holding tanks. Most bycatch was discarded overboard, al- 

 though some fishermen retained certain species, including 

 seahorses, for sale as aquarium fishes. 



Bycatch sampling and data set description 



Data on seahorse bycatch in the live-bait shrimp fishery 

 were collected on 95 fishing nights, from June to August 

 1998 and from June to July 1999, using three methods: 1) 

 we sampled bycatch onboard on 50 nights; 2) we recorded 

 seahorse bycatch data onshore on 14 nights from fishers 

 who retained seahorses to sell; and 3) we received data 

 from fishermen on their seahorse catches (including loca- 

 tion, time, number of trawls, and number of seahorses 

 per trawl) on a total of 31 nights. Onboard sampling was 

 semistratified in that we targeted our sampling to cover all 

 lunar and tidal phases and a variety of areas. However, we 

 were dependent on fishersmen's decisions about the time 

 and location of tows. We also collected anecdotal informa- 

 tion from 14 experienced fishermen about seahorse catches 

 over time. 



During onboard sampling, we recorded the number of 

 seahorses caught, start and end time of trawl, depth and lo- 

 cation (Loran co-ordinates) of trawl, tidal and lunar phases, 

 and presence or absence of all bycatch species, including 

 biogenic habitat species. Hippocampus erectus found in 

 the catch were placed in a container of surface water 

 while measurements were made. They were then released, 

 except when fishermen chose to retain them for sale. We 

 measured, weighed, determined the sex, and recorded the 

 life history stage, reproductive status, and any injury for 

 each seahorse. Measurements were taken according to 

 Lourie et al. (1999) and included standard length, defined 

 as the length from the tip of the snout to the opercular 

 ridge and from the opercular ridge to straightened tail tip. 

 Seahorses that had lost tail rings were not included in the 

 length analysis. Unless precluded by logistic constraints, 

 wet weights were obtained onboard by using a 60-g Pesola 

 spring scale and onshore by using a 200-g Ohaus electronic 

 balance. Adult males were distinguished from females and 

 juveniles by the presence of a brood pouch. The standard 

 length of the smallest seahorse with a brood pouch (105.3 

 mm) was used as the division between adults andjuveniles 

 with the assumption that males and females matured at 

 the same size. Such an assumption may overestimate the 



