Sicyonia sp.; and the crabs Albunea and Pinnixa. All 

 comparisons of longspine porgy diets were 

 significantly correlated, except between age-0 in 45- 

 73 m waters and age-I in 18-44 m waters. Polychaetes 

 were the primary food in all age/depth categories, 

 and animal fragments and detritus were also abun- 

 dant. The main differences between age classes were 

 that age-0 longspine porgy consumed more copepods 

 but less crabs than age-I individuals. 



Discussion 



The major foods identified in this study are general- 

 ly similar to the foods of these seven species de- 

 scribed by other investigations in the Gulf of Mexico. 

 Gunter (1945), Knapp (1949), and Darnell (1958) 

 reported that hardhead catfish consumed crabs, 

 shrimps, and detritus in estuaries, but provided 

 neither age nor habitat-related analyses of their data. 

 Divita et al. (1983), using samples collected at the 

 same time as ours but analyzing diets by percent fre- 

 quency of occurrence, reported differences between 

 age-0 and age-I hardhead catfish diets in 9-17 m 

 waters. They found that, in comparison with age-0 in- 

 dividuals, age-I fish consumed holothurians, fishes, 

 bivalves, shrimps, and detritus more frequently and 

 crabs, stomatopods, and polychaetes less frequently. 

 Our results (based on percent dry weight) contrast in 

 that, for the age-I catfish diet, shrimps were less im- 

 portant and stomatopods were more important than 

 in the age-0 diet in 7-17 m waters. 



Two studies have investigated the diet of longspine 

 porgy, the results of which generally agree with ours. 

 Henwood et al. (1978), summarizing data over a 130 

 m depth range and ages and I, found polychaetes, 

 shrimps, and crabs were the most abundant foods. 

 Rogers (1977) analyzed longspine porgy diets in four 

 arbitrary size classes (two each in ages and I) and 

 three arbitrary depth zones (3-18, 19-55, and 56-200 

 m), but not by age/depth combinations. He found 

 that both ages preferred polychaetes and that age-0 

 porgy stomachs contained more animal fragments 

 and detritus than did age-I porgy stomachs, as we 

 report. In contrast, though, Rogers noted that age-I 

 longspine porgy preyed extensively on fishes causing 

 midshelf diets to differ from outer shelf diets. The 

 differences between our reports are probably due to 

 Rogers' year-round sampling over a wide area (Tex- 

 as, Louisiana, and Mississippi shelf). 



The diets of sand and silver seatrouts were also ex- 

 amined by Rogers (1977). His three size classes of 

 sand seatrout were all age-0 fish (26-100 mm SL) 

 which consumed fishes, shrimps, and squids, preyed 

 mainly upon fishes in shallow waters and squids in 



moderate depths, thus agreeing with our data. His 

 largest size class of silver seatrout (76-175 mm SL, 

 ages and I combined) was piscivorous and is com- 

 parable to our findings, but no age/depth data 

 were given. 



We found the Atlantic croaker diet was influenced 

 by both age and depth of capture. This is the likely 

 reason for the variety of primary foods previously 

 reported for this species. Chen (1976) examined age- 

 and age-I Atlantic croaker (data summed over 9-73 

 m depths) and reported similar diets of primarily 

 organic and inorganic matter with lesser amounts of 

 crabs, shrimps, and stomatopods. Although the in- 

 fluence of depth was not discussed, she proposed 

 that diet variations were substrate-related. Rogers 

 ( 1 977) noted that polychaetes and stomatopods were 

 the main foods of age-0 Atlantic croaker in shallow 

 and moderate depths. Overstreet and Heard (1978) 

 documented both size and depth of capture as fac- 

 tors independently affecting Atlantic croaker diets: 

 small individuals (76-195 mm SL) consumed more 

 polychaetes and fewer molluscs, crustaceans, and 

 fishes than did large individuals (200-351 mm), and 

 fish from shallow water (11-29 m) consumed more 

 polychaetes and fishes and fewer crustaceans than 

 fish from deep water (30-90 m). However, their com- 

 parisons apparently included two age classes in each 

 size range, formed arbitrary depth zones, and did not 

 examine age/depth as a combined influence. Divita 

 et al. (1983) found detritus to be the most frequently 

 observed item in both age-0 and age-I Atlantic 

 croaker stomachs from both shallow- and midshelf, 

 and observed no differences in diets among age/ 

 depth categories. The available data thus indicate 

 that Atlantic croaker are highly opportunistic in their 

 feeding strategy, which is readily influenced by age, 

 depth, season, and, probably, site. 



Our results agree with previous reports concerning 

 offshore spot and Atlantic cutlassfish diets. Chen 

 (1976) examined age-I spot from 9-27 m depths and 

 found inorganic and organic matter, polychaetes, and 

 shrimps were the primary foods. Mericas (1981) 

 noted Atlantic cutlassfish were piscivorous from late 

 age into age III. 



We conclude that the degree to which age and depth 

 of capture simultaneously affect fish diets depends 

 upon the species examined: Atlantic croaker are 

 highly influenced and longspine porgy are only slight- 

 ly influenced. This variation between species may 

 have been due to the age/depth distributions of the 

 fishes during the limited collecting period, and thus 

 seasonal collections should be compared. It is also 

 possible that fishes had fed in one depth zone and 

 moved into the adjacent depth zone prior to capture. 



646 



