CHAPTER 4 

 FISHES 



4.1 INTRODUCTION 



Fishes migrate onto tidal flats dur- 

 ing flood tides and retreat during ebb 

 tides. A few species, such as stickle- 

 backs and mummichogs, remain in tidal 

 creeks during ebb tide. It is difficult, 

 therefore, to identify which species of 

 fish actually are representative of tidal 

 flat habitats since they may utilize these 

 areas only during portions of their life 

 cycle (e.g., as a nursery ground), on a 

 daily or seasonal basis for spawning or 

 pursuing preferred prey items, or through- 

 out their entire life span. In addition, 

 tidal flats are not closed ecological sys- 

 tems; rather, they are bounded by and 

 intricately linked to other coastal habi- 

 tats such as salt marshes, estuaries, and 

 eelgrass beds. Actively moving organisms 

 such as fishes can and do readily move 

 from habitat to habitat during the course 

 of feeding and reproducing. Few species 

 are exclusive inhabitants of tidal flats 

 but are more often found in other habitats 

 adjacent to tidal flats (e.g., deeper 

 waters, rocky outcrops) that afford more 

 protection. Generally, fish utilizing 

 tidal flats are estuarine species, juve- 

 nile and adult fishes from deeper marine 

 waters that use the sites as nursery 

 grounds and feeding sites, and diadromous 

 species that cross the habitat during 

 migrations to and from spawning sites or 

 wintering areas. 



The approach taken to describe the 

 fishes associated with New England tidal 

 flats has focused on those representative 

 species one would be most likely to 

 encounter when sampling. Commercially 

 important species (for which the most life 

 history information is available) and non- 

 commercial species (for which there are 

 sporadic sampling and life history data) 

 are viewed collectively. In many publica- 

 tions, the two groups have been treated 

 separately. 



Appendix II gives names and related 

 life history information for fish species 

 common throughout the tidal flats of the 

 New England coastal zone. Species were 

 selected from Bigelow and Schroeder 

 (1953), Leim and Scott (1966), and Thomson 

 et al. (1971) who provide extensive inven- 

 tories for the regions they cover. Scien- 

 tific and common names are those cited by 

 Robins et al. (1980). Distributional 

 patterns, spawning periodicity, and food 

 habits have been accumulated for each spe- 

 cies from several sources and are as gen- 

 eral or specific as the cited authors have 

 reported. 



4.2 TROPHIC RELATIONSHIPS 



A broad spectrum of trophic roles is 

 displayed by fishes inhabiting the New 

 England coastal zone and it is possible to 

 divide them into generalized feeding cate- 

 gories (e.g., demersal feeders, predators, 

 planktivores). Aside from menhaden (an 

 exclusive herbivorous planktivore) and 

 several species of omnivores and grazers, 

 most fish appear to be carnivorous. Al- 

 though Appendix II shows that many species 

 display wide dietary preferences, several 

 studies have demonstrated that food selec- 

 tion does occur on a community level. 

 Demersal and pelagic fishes apparently 

 select food by size and type as well as 

 forage at different times or in different 

 habitats (Richards et al. 1963; Tyler 

 1972; Maurer 1976). A change in food 

 preference with age (size) appears to be 

 the general rule (Appendix II) with many 

 of the juvenile stages feeding as plank- 

 tivores regardless of later dietary 

 specialization. This feature is particu- 

 larly germane to a discussion of trophic 

 relationships on tidal flats because many 

 fish inhabiting these areas are juvenile 

 forms. There have been several expla- 

 nations for age- or size-related changes 

 in feeding behavior. Changing dietary 



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